UC-NRLF 


T  BOOK 


'i 


DEF 


Gift 


No. 


N 

f 

r 


LIPPINCOTT'S   PHTSIQLOGiES 


THE  FIRST  BOOK 

OF 

ANATOMY,  PHYSIOLOGY 

AND  » 

HYGIENE 

OF  THE  HUMAN  BODY 

FOR    PUPILS    IN    THE    LOWER    GRADES 
BY 

J.  A.  CULLER,  PH.D. 

PROFESSOR     OF    PHYSICS     IN     MIAMI     UNIVERSITY,     OXFORD,     OHIO 


PHILADELPHIA  AND  LONDON 

J.  B.  LIPPINCOTT   COMPANY 


•     . 


C$4 


COPYRIGHT,  1904 

BY 

J.  B.  LIPPINCOTT  COMPANY 


Electrotyped  and  Printed  by 
J.  B.  Lippincott  Company,  Philadelphia,  U.S.A. 


PREFACE 


WHAT  to  present  and  how  to  present  it  is 
the  chief  concern  of  the  teacher  of  physiology 
in  the  lower  grades.  Without  a  book,  the 
work  in  this  subject  is  apt  to  be  neglected  or 
only  fragmentary. 

As  soon  as  a  pupil  has  learned  to  read 
fairly  well,  he  can  profitably  use  a  primary 
book  in  physiology.  Such  a  book  should 
make  the  study  of  the  subject  interesting, 
definite,  and  systematic. 

The  aim  of  this  book  is  to  supply  such  a 
need.  The  language  and  manner  of  expres- 
sion are  such  as  children  can  understand.  The 
simple  facts  only  are  presented,  much  being 
left  unsaid,  and  yet  definite  and  direct  infor- 
mation is  given  as  far  as  it  goes.  The  ability 
of  children  to  understand  a  subject  such  as 
this  is  often  underestimated. 


4  PREFACE 

Boys  and  girls  are  always  more  interested 
when  they  are  given  something  to  do  along 
with  the  study  of  the  book.  In  several  places 
in  this  book  directions  and  suggestions  are 
made  to  this  end,  and  we  suggest  that  the 
teacher  add  to  the  list  as  time  and  opportu- 
nity permit. 

One  aim  in  this  book  is  to  get  the  pupil  to 
feel  that  he  is  studying  about  himself.  If  he 
can  be  made  to  realize,  as  far  as  a  child  can, 
how  wonderfully  and  delicately  his  body  is 
made,  so  that  he  begins  to  wonder  and  admire, 
then  the  great  aim  of  this  early  study  is 
accomplished.  This  counts  for  much  more 
than  nomenclature. 

The  effect  of  alcohol  and  narcotics  is  given 
along  with  the  study  of  the  various  parts  and 
organs  of  the  body.  The  evils  of  intemper- 
ance are  a  proper  study  in  public  schools  that 
seek  to  train  up  citizens  who  will  be  strong 
mentally,  morally,  and  physically,  and  there 
is  no  excuse  for  its  neglect  in  connection 
with  this  subject. 

Several   stories    based  on    facts  of   history 


PREFACE  5 

or  experience  are  given  to  fix  the  statements 
that  have  just  preceded.  While  story-telling 
may  easily  be  overdone,  yet  the  right  kind 
of  a  story  at  the  right  time  is  a  most  efficient 
means  of  education. 

We  acknowledge  our  indebtedness  to  Ginn 
&  Co.  for  Figs.  24  and  30  from  Dr.  Blaisdell's 
"  Physiology,"  and  also  to  the  J.  B.  Lippincott 
Company  for  Figs.  15  and  25  from  Cutter's 
"  Physiology."  Also  to  all  others  who  contri- 
buted in  any  way  to  the  preparation  of  this 
book. 

J.  A.  C. 


CONTENTS 

¥ 

CHAPTER  PAGB 

I.  WHY  WE  STUDY  PHYSIOLOGY       .         .          .11 

II.  BONES        . 17 

III.  MUSCLES 29 

IV.  FOOD 40 

V.  DIGESTION .48 

VI.   BLOOD 64 

VII.   BREATHING 75 

VIII.   THE  SKIN 95 

IX.   EXCRETION         .         .         .         .         .         .107 

X.   THE  BRAIN,   SPINAL  CORD,  AND  NERVES     .    in 
XI.  THE  SENSES 131 


PAGE 


ILLUSTRATIONS 

¥ 

FIG. 

1.  A  healthy  body       .  .          .          .          .          .12 

2.  Two  pots  of  flowers  .          .          .          .          .12 

3.  The  framework       .  .          .          .          .  17 

4.  Bones  of  hand  and  arm  .          .          .          .18 

5.  The  femur     .          .  .          .          .          .  19 

6.  Bones  of  a  boy's  hand  .....      22 

7.  Bones  of  a  man's  hand  .          .          .         .  23 

8.  Bone  tied  in  a  knot  .          .          .          .  25 

9.  Cross-section  of  bone  .....      26 

10.  Tendons  of  hand  .          .          .          .  32 

11.  Muscle  ....  34 

12.  An  old  well  ...  -45 

13.  Section  of  front  tooth 49 

14.  A  girl  laughing       .  .      50 

15.  Stomach  and  intestines   .  .      53 

16.  Section  of  intestine          .          .          .         .  56 

17.  Villi  of  intestine     .          .         .         .         .          -57 

18.  The  heart 65 

19.  Counting  the  pulse 68 

20.  Veins  in  the  arm    ......      70 


io  ILLUSTRATIONS 

FIG.  PAGE 

21.  Red  corpuscles       .          .         .         .         .         .71 

22.  Fine  silk        .          .          .          .          .          .          .72 

23.  Candle  flame  ......      76 

24.  Air-tubes       ...  ...      78 

25.  Lungs  .  ....      79 

26.  Breath  and  candle  flame  .          .          .          .84 

27.  A  soap-bubble        ......      88 

28.  Water-jug 91 

29.  Bee  sting       .......     98 

30.  The  skin        ....  .          .    100 

3 1 .  The  brain      .          .          .          .  .          .112 

32.  A  vertebra     .  ...                    .    113 

33.  A  skull           .          .  .          .                     .118 

34.  Before  and  after  long  practice  .          .          .121 

35.  Demosthenes  .          .          .          .          .          .124 

36.  The  eyes 132 

37.  Section  of  eye         ......    132 

38.  The  ear 135 


FIRST   BOOK  OF  PHYSIOLOGY 


CHAPTER    I 

WHY   WE   STUDY   PHYSIOLOGY 

This  book  should  be  very  interesting,  for  it 
is  all  about  ourselves. 

We  ought  to  know  something  about  our 
bodies,  so  that  we  may  be  able  to  take  care  of 
them. 

Every  boy  and  girl  wants  to  grow  up  strong 
and  healthy. 

There  are  some  things  that  are  good  for  us, 
and  we  ought  to  know  what  they  are  ;  then 
there  are  other  things  that  will  make  us  weak 
and  sickly,  and  we  must  know  how  to  avoid 
them. 

Here  is  the  picture  of  a  young  man  who 
has  always  taken  good  care  of  his  health. 

You  can  see  that  he  is  strong. 

He  can  do  a  great  deal  of  work  without 
getting  very  tired,  and  he  is  always  in  good 
humor  and  is  happy. 

People  like  to  do  business  with  him. 

ii 


12 


FIRST   BOOK   OF   PHYSIOLOGY 


He  is,,  getting  along  better  in  the  world  than 
some  others  who  had  an  equal  chance,  but  did 


I.  —A  healthy  body. 

not    care    for  their    health    when    they  were 
younger. 


2. — Two  pots  of  flowers. 

In  the  second  picture  you  see  two  sets  of 
plants.  One  of  them  is  far  ahead  of  the  other, 
and  yet  they  had  an  equal  start.  For  a  while 


WHY    WE    STUDY    PHYSIOLOGY  13 

at  first  we  could  not  see  any  difference  be- 
tween them. 

The  larger  bunch  grew  in  rich  ground  and 
had  good  air  and  sunshine. 

The  other  one  was  planted  in  poor  ground 
and  so  it  could  not  get  enough  food,  and  it 
was  in  a  place  where  it  could  not  get  the  right 
amount  of  light. 

It  is  no  fault  of  these  small  plants  that  they 
are  not  as  strong  and  large  as  the  others,  for 
they  could  not  help  themselves.  But  it  is 
often  the  fault  of  boys  and  girls  and  men  and 
women  when  they  are  not  healthy,  for  either 
they  did  not  know  what  they  ought  to  do  or 
else  they  did  not  do  it. 

Most  people  who  are  not  healthy  have  no- 
body but  themselves  to  blame. 

The  doctor  may  be  able  to  help  us  when  we 
are  sick,  but  he  cannot  keep  us  well.  We 
must  do  that  ourselves. 

When  you  know  what  a  wonderful  body 
you  have  and  how  nicely  it  works,  you  will 
surely  do  all  you  can  to  help  it  and  nothing 
to  hinder  it. 

There  are  three  things  that  we  will  study  in 
this  book. 

First,  we  will  try  to  learn  what  the  different 
parts  of  the  body  are  and  what  they  are  like. 


14  FIRST   BOOK   OF   PHYSIOLOGY 

Second,  what  these  different  parts  will  do 
for  us. 

Third,  how  to  care  for  all  the  parts  of  the 
body  that  they  may  do  their  work  well. 

You  have  all  at  some  time  taken  a  ride  on 
a  railroad  train.  You  noticed  that  the  train 
was  pulled  along  by  a  great  engine  in  front. 

Up  in  the  engine  sat  a  man  who  was  called 
the  engineer.  Now,  what  kind  of  a  man  do 
you  think  would  make  the  best  engineer?  I 
think  you  would  all  say  it  would  be  the  man 
who  knew  all  the  parts  of  the  engine  and  what 
each  part  should  do.  But,  most  important  of 
all,  he  should  know  how  to  manage  and  care 
for  his  engine  so  that  it  will  pull  the  train 
swiftly  and  safely  from  town  to  town  until  it 
reaches  the  end  of  its  journey. 

These  engineers  go  to  school  and  study 
hard  to  learn  how  to  manage  their  engines. 
Certainly  we  should  be  willing  to  learn  the 
best  way  to  use  and  care  for  our  bodies  so  that 
they  may  do  their  work  well. 

The  different  parts  of  our  bodies  do  different 
kinds  of  work. 

No  doubt  you  have  all  seen  a  printing-press 
at  work.  Maybe  it  was  printing  one  of  the 
papers  that  the  boys  sell  on  the  streets.  You 


WHY    WE    STUDY    PHYSIOLOGY  15 

saw  that  there  was  a  strong  frame  of  iron  to 
hold  all  the  parts  of  the  press  in  their  proper 
places.  One  part  of  the  machine  drew  in  a 
large  sheet  of  white  paper.  Another  part 
spread  the  ink  on  the  type.  Then  a  large 
steel  roller  pressed  the  paper  down  on  the 
metal  letters.  Then  another  part  of  the  ma- 
chine-took the  printed  paper  and  folded  it  up 
ready  for  the  boy  to  take  under  his  arm  and 
run  out  into  the  street  to  sell. 

You  noticed  that  there  was  a  great  number 
of  wheels  and  levers  and  rollers. 

Each  one  had  its  own  work  to  do,  and  all 
these  parts  had  to  work  together  to  make  one 
complete  machine  called  the  printing-press. 

If  any  one  part  failed  to  do  its  work,  then 
the  whole  machine  would  have  to  stop  till  this 
part  could  be  fixed. 

In  the  same  way  our  bodies  are  made  up 
of  many  different  parts,  and  each  part  has  its 
own  kind  of  work  to  do.  We  have  a  strong 
framework  made  of  bone,  and  this  holds  the 
other  parts  of  our  bodies  in  their  proper 
places. 

The  heart  has  nothing  to  do  but  make 
the  blood  go  around  and  around  through  the 
body.  The  lungs  only  breathe  in  the  air 
which  we  need.  Our  muscles  move  us  about 


1 6  FIRST   BOOK    OF    PHYSIOLOGY 

from  place  to  place.  Our  minds  think.  Our 
eyes  can  do  nothing"  but  see.  •  Our  ears  can 
do  nothing  but  hear. 

There  are  a  great  number  of  parts  in  the 
human  body,  and  when  they  all  work  together 
and  each  part  does  what  it  ought  to  do,  then 
the  body  is  in  good  health. 

The  man  who  owns  the  printing-press  that 
we  just  talked  about  takes  good  care  of  it,  so 
that  it  may  last  a  long  time.  Every  boy  and 
girl  should  know  how  to  take  care  of  their 
bodies,  so  that  they,  too,  will  be  strong  and 
will  last  a  long  time. 

In  the  next  lessons  we  will  try  to  learn  some 
interesting  things  about  this  body  of  ours. 

Questions. 

1.  Why  can  a  man  get  along  better  when  his  health  is 
good  ? 

2.  Tell  about  the  two  pots  of  plants. 

3.  How  is  physiology  a  useful  study  ? 

4.  What  three  things  are  to  be  studied  in  this  book  ? 

5.  Tell  about  the  engineer  on  a  railroad  train.      How  did 
he  learn  to  manage  his  engine  ? 

6.  Tell  how  a  printing-press  works. 

7.  How  are  our  bodies  like  a  printing-press  ? 

8.  When  is  the  body  in  good  health  ? 

9.  Name  some  things  which  you  think  are  good  for  the 
health. 

10.  Name  some  things  that  do  the  body  harm. 


CHAPTER    II 

THE    BONES 

EVERY  animal  has  some  kind  of  a  frame- 
work to  hold  its  body  in  shape  and  to  make  it 
strong.  Some  have  this  framework  on  the 
outside  and  some  on  the  inside.  A  crab  has 
no  bones  on  the  inside  of  its  body,  but  it  is 
covered  by  a  hard  crust.  An  oyster  has  a 
strong,  hard  shell  on  the  outside  of  its  body. 
A  turtle  has  a  strong  shell  on  the  outside  and 
also  bones  on  the  inside. 

A  man  and  all  the  larger  animals  have  their 
framework  on  the  inside. 


3.  —  The  framework. 

You  see  in  the  picture  the  framework  of  a 
monkey.      The  monkey  is  a  very  lively  crea- 


i8  FIRST   BOOK   OF    PHYSIOLOGY 

ture,  and  can  climb  a  tree  or  jump  a  long  way 
from  limb  to  limb  ;  but  if  he  did  not  have  tiis 
framework  of  bone  he  would  be  nearly  as 
slow  as  a  snail. 

We  have  inside  of  our  bodies  a  framework 
of  bone  much  like  that  of  the  monkey,  only 
our  bones  are  larger  and  stronger  and  we 
stand  up  straight. 

Let  us  try  to  find  some  of  the  bones  of  our 
body.  How  many  bones  have  you  in  each 


4. — Bones  of  hand  and  arm. 

finger  ?  How  many  in  the  fingers  and  thumbs 
of  both  hands?  Can  you  feel  any  bones  in 
your  wrist?  Try.  You  see  in  the  picture 
that  you  have  two  bones  above  the  wrist  and 
these  run  all  the  way  to  the  elbow. 

Feel  for  them  in  your  own  arm.  Count  the 
bones  of  the  wrist  as  you  see  them  in  the 
picture. 

Feel  for  a  bone  in  your  arm  above  the  elbow. 


THE    BONES  19 

There  is  only  one  bone  here,  but  it  is  a  long 
and  stronor  one. 

o 

Try  to  find  your  collar-bone  and  your 
shoulder-blade.  You  can  easily  find  your  ribs, 
for  they  are  near  the  outside  and  extend  from 
the  backbone  around  the  body  to  the  breast- 
bone in  front. 

In  the  leg  is  the  largest  and  strongest  bone  in 
the  body.  It  is  between  the  hip  and  the  knee. 


5. — The  femur. 

In  the  picture  you  can  see  how  it  looks. 
This  bone  needs  to  be  strong,  for  it  has  to 
hold  up  the  weight  of  the  body,  and  also  any 
other  weight  that  a  man  may  carry  in  his  arms 
or  on  his  shoulder. 


20  FIRST   BOOK   OF    PHYSIOLOGY 

From  the  knee  down  to  the  ankle  there  are 
two  bones  again,  just  as  we  found  two  in  the 
arm  lying  side  by  side. 

The  bones  of  the  ankle  and  foot  are  about 
like  those  of  the  wrist  and  hand. 

Kinds  of  bones. 

There  are  about  two  hundred  different 
bones  in  the  human  body.  Some  of  them  are 
called  long  bones,  and  this  is  the  kind  you 
have  in  your  arms  and  legs.  Some  are  called 
short  bones.  You  have  these  in  your  wrist 
and  ankle.  Others  are  the  flat  bones,  such  as 
are  found  in  the  skull  and  the  shoulder-blade. 
The  irregular  bones  form  a  fourth  kind. 
These  are  such  as  the  jaw-bone  and  backbone. 

Bones  are  made  in  a  great  many  different 
sizes  and  shapes  so  that  they  may  fit  in  where 
they  belong  and  may  be  most  useful  to  us. 

Joints. 

You  can  see  that  it  would  not  do  to  have 
only  one  long  bone  in  the  arm  or  leg,  for  then 
we  could  not  bend  the  arm  at  the  elbow  or  the 
leg  at  the  knee. 

You  have  counted  and  found  that  there  are 
many  bones  in  the  hand,  and  so  there  can  be 
many  joints.  Our  hands  are  very  useful  to 


THE   BONES  21 

us  because  they  have  so  many  joints  and  so 
can  bend  in  so  many  different  ways. 

Bend  your  arm  at  the  elbow.  You  find 
that  you  can  bend  the  arm  in  and  out,  but  you 
cannot  bend  it  sideways.  The  elbow-joint 
acts  much  like  the  hinge  on  a  door,  and  so  it 
is  called  a  hinge-joint.  The  knee  is  the  same 
kind  of  joint. 

Now  swing  your  right  arm  about,  using  the 
joint  at  the  shoulder.  Feel  with  your  other 
hand  and  see  if  you  can  tell  how  this  joint 
works.  Try  this  at  home  where  you  can  take 
off  your  clothes.  This  is  called  a  ball-and- 
socket  joint.  The  same  kind  of  joint  is  found 
in  the  hips.  In  picture  5  you  can  see  the  ball 
at  the  upper  end  of  the  bone. 

Our  backbones  are  made  up  of  thirty-three 
different  bones  placed  one  on  top  of  the  other. 
This  allows  us  to  bend  the  body  forward  and 
backward  or  sideways. 

How  would  you  have  to  act  if  the  backbone 
were  one  long,  solid  bone  ? 

How  the  joints  are  made. 

Where  the  bones  come  together  at  the  ends 
they  are  bound  by  very  strong  bands  to  keep 
them  together  and  in  their  right  place.  Some- 
times a  bone  is  pushed  out  of  place  by  acci- 


22 


FIRST   BOOK   OF   PHYSIOLOGY 


dent,  and  then  the  doctor  has  to  be  called  in 
to  set  it  right. 

In  children  a  very  soft  cushion  is  found  be- 
tween the  ends  of  the  bones  at  all  the  joints. 
This  is  called  cartilage. 

In  older  persons  this  cushion  of  cartilage  is 
not  nearly  so  thick,  but  the  bones  never  come 
close  together. 


6. — Bones  of  a  boy's  hand. 


This  is  a  picture  of  the  hand  of  a  boy  who  is 
ten  years  old.  You  see  there  is  a  wide  space 
between  the  bones  in  the  wrist  and  at  the  joints 
of  the  fingers.  These  spaces  are  filled  with 
soft,  tough  cartilage.  Some  of  the  cartilage 
is  turning  to  bone,  as  you  can  tell  by  the  thin 
buttons  of  bone  which  you  see  in  each  joint. 


THE   BONES  23 

By  the  time  the  boy  is  about  fifteen  years 
of  age  these  buttons  will  grow  thicker,  and 
will  fasten  themselves  to  the  end  of  the  bones, 
and  then  the  hand  will  be  as  you  see  it  in  pic- 
ture 7. 


7. — Bones  of  a  man's  hand. 

Between  the  many  bones  of  the  backbone 
there  are  soft  cushions  of  this  sort.  They  act 
like  the  springs  under  a  buggy,  and  prevent 
any  sudden  jolting  of  the  body  and  head  when 
we  walk  or  run  or  jump. 

What  bone  is  made  of. 

If  you  will  try  you  can  find  a  large  bone  out 
in  a  field  or  in  a  boneyard.  Look  at  it  closely. 
You  will  find  that  it  is  very  hard  and  is  hollow. 


24  FIRST   BOOK   OF    PHYSIOLOGY 

When  it  was  alive  it  was  filled  with  a  fatty 
substance  called  marrow. 

Also,  get  a  piece  of  fresh  bone  from  your 
butcher.  Try  to  cut  it  with  your  knife.  You 
find  it  very  hard,  but  it  has  soft  matter  mixed 
with  it  which  makes  it  tough.  In  all  very 
young  animals,  as  well  as  in  boys  and  girls, 
there  is  more  soft  matter  than  hard.  As  we 
grow  older  the  bones  get  harder  and  harder. 

The  substance  that  makes  the  bone  hard 
is  lime.  The  bones  of  small  children  are  soft 
because  there  is  not  much  lime  in  them.  The 
ear  is  just  like  bone,  but  it  has  no  lime  in  it,  and 
so  you  can  bend  your  ear  without  breaking  it. 

One  tribe  of  Indians  had  a  very  foolish 
notion  that  it  was  nice  to  have  the  tops  of 
their  heads  flat.  So  when  their  children  were 
very  young  they  would  press  a  board  down 
on  the  tops  of  their  heads  and  tie  it  there  till 
the  bones  of  the  skull  would  get  lime  into 
them  and  then  they  would  stay  flat. 

You  can  see  that  you  ought  to  be  very  care- 
ful how  you  stand  and  sit  and  dress  while  you 
are  young.  After  a  while  the  bones  get  hard 
and  then  you  cannot  change  them.  Boys  and 
girls  should  stand  straight  and  sit  up  straight 
and  keep  their  shoulders  up.  It  looks  much 
better,  and  it  is  better  for  the  health. 


THE   BONES  25 

Something  for  you  to  do. 

The  next  time  you  have  chicken  for  dinner 
save  the  long  bone  of  the  chicken's  leg  and 
put  it  into  a  bottle.  Pour  in  enough  water  to 
cover  the  bone.  Then  pour  in  about  three 
tablespoonfuls  of  muriatic  acid.  Leave  it 
there  for  one  day.  Now  take  the  bone  out 
and  you  will  find  it  so  soft  that  you  can  tie  it 
into  a  knot. 

The  acid  has  eaten  away  all  the  lime  and 
left  all  the  soft  part.  Try  it.  In  the  picture 
you  see  the  rib  of  a  lamb  that  was  treated 
that  way  and  then  tied  into  a  knot. 


8. — Bone  tied  in  a  knot. 

Now  get  a  bone  that  has  been  used  in  mak- 
ing soup.  Put  it  into  the  stove  with  the  hot 
coals  and  leave  it  there  for  a  few  hours.  Then 
take  it  out  and  you  will  find  that  all  the  soft 
part  has  been  burned  away  and  only  the  lime 
is  left.  Try  it. 

Broken  bones. 

The  bones  of  grown  people  are  hard  and 
strong,  and  yet  they  will  bend  a  little.  In 
children  they  will  bend  a  great  deal,  but  are 


26  FIRST   BOOK    OF    PHYSIOLOGY 

often  broken.  Bones  are  often  broken  by  a 
fall  down-stairs  or  from  a  tree,  o'r  by  slipping 
and  falling  on  a  leg  or  arm.  When  this  hap- 
pens a  surgeon  must  be  called  in  to  set  the 
bones  in  place  again.  You  must  then  keep 
the  broken  part  very  quiet  for  three  or  four 
weeks  or  more  until  the  broken  ends  grow 
together. 

If  you  have  good  health  and  are  careful  the 
ends  will  grow  together  again,  but  the  bone 
will  never  be  quite  so  good  as  it  was  before. 


How  bones  grow. 

The  bone  is  alive  just  like  flesh  and  other 
parts  of  the  body.  The  picture  shows  how  a 
thin  slice  of  bone  looks  in  a  microscope. 


THE   BONES  27 

The  slice  was  cut  across  the  bone.  You 
see  that  it  is  full  of  small  holes.  Blood-tubes 
pass  through  these  holes  and  carry  blood  to 
all  parts  of  the  bone.  That  is  the  way  the 
bone  gets  its  food. 

Now  you  can  see  that  the  blood  should 
have  in  it  what  the  bone  needs.  If  the  bones 
cannot  get  from  the  blood  the  kind  of  food 
they  need,  they  will  not  grow  and  make  a 
strong  framework  for  our  bodies. 

Things  that  harm  the  bones. 

You  have  just  seen  that  the  bone  is  alive, 
and  so  of  course  it  can  become  diseased.  The 
doctors  all  tell  us  that  tobacco  has  a  very  bad 
effect  on  the  bones  of  a  growing  boy.  The 
boy  who  uses  tobacco  will  never  be  as  large 
and  strong  as  he  would  have  been  without  it. 
His  bones  will  not  grow  well  because  he  is 
feeding  them  poison  instead  of  pure  blood. 
In  this  way  many  boys  are  stunting  their 
growth  by  the  use  of  cigarettes. 

Any  drink,  too,  that  has  alcohol  in  it  is  a 
poison  to  the  blood.  One  who  uses  such  a 
drink  cannot  be  healthy. 


28  FIRST   BOOK   OF    PHYSIOLOGY 

Questions. 

1.  What  kind  of  framework  has  a  crab  ?    An  oyster  ?     A 
turtle  ? 

2.  What  kind  of  framework  does  a  monkey  have  ?     Of 
what  use  is  it  ? 

3.  What  kind  of  framework  is  in  the  human  body  ? 

4.  How  many  bones  in  the  whole  hand  ? 

5.  Where  is  the  largest  and  strongest  bone  in  the  body  ? 
Why  is  it  so  strong  ? 

6.  How  many  bones  in  the  whole  body  ? 

7.  Name  four  kinds  of  bones. 

8.  W7hat  is  the  use  of  joints  ? 

9.  Name  two  kinds  of  joints  and  give  an  example  of  each 
kind. 

10.  How  do  the  joints  in  the  boy's  hand  differ  from  those 
in  the  hand  of  the  man  ? 

11.  What  makes  bone  hard  ? 

12.  Why  are  the  bones  of  young  children  soft  ? 

13.  Have  you  tried  to  tie  a  bone  in  a  knot  ? 

14.  What  should  be  done  when  a  bone  is  broken  ? 

15.  What  does  a  cross-section  of  a  bone  look  like  under 
a  microscope  ?     What  are  the  holes  for  ? 

1 6.  What  are  some  things  that  harm  bones  ? 

17.  Could  you  throw  a  ball  if  there  were  no  bones  in  your 
arm  ? 


CHAPTER    III 

MUSCLES 

IN  the  last  lesson  we  learned  that  the  bones 
are  the  framework  of  the  body.  They  keep 
the  body  in  shape.  They  make  it  strong. 
They  protect  some  parts  of  the  body  from 
harm.  They  help  us  to  make  swift  motions. 
But  the  bones  cannot  move  themselves,  and  a 
man  would  not  be  of  much  use  if  he  could 
not  move  about.  You  know  that  you  can 
move  your  body  in  all  sorts  of  ways.  How 
do  you  do  this  ?  We  will  try  to  tell  you  in 
this  lesson. 

Now  look  again  at  the  first  picture  in  this 
book.  You  cannot  see  this  man's  bones  be- 
cause they  are  all  covered  up  with  muscles. 
On  his  arm  you  see  a  large  bundle  of  muscles. 
They  make  his  arm  strong. 

Let  us  try  to  find  some  muscles  on  our  own 
bodies.  Put  your  hands  on  your  cheeks  and 
close  your  teeth  together.  Bite  the  teeth  to- 
gether several  times  while  you  feel  for  the 
muscles  in  the  cheeks.  Keep  on  doing  this 

till  you  know  just  about  where  the  muscles  are, 

29 


30  FIRST   BOOK   OF    PHYSIOLOGY 

and  how  strong  they  are.  The  upper  ends  of 
these  muscles  are  fastened  to  the  skull,  and  :he 
lower  ends  to  the  lower  jaw-bone.  When  we 
make  them  shorter  they  pull  the  jaw  up.  In 
this  way  you  can  bite  off  your  food  and  chew  it. 

There  are  other  muscles  around  the  mouth 
so  that  you  can  pull  your  lips  back  and  show 
your  teeth,  or  you  can  draw  your  lips  to  a  small 
round  hole  as  boys  do  when  they  whistle. 

Then  there  is  another  muscle  which  is  fas- 
tened to  each  corner  of  the  mouth,  and  we 
use  it  when  we  laugh  or  smile. 

There  are  a  great  number  of  muscles  in 
the  face,  and  we  can  use  them  just  as  we  like. 
Boys  and  girls  can  make  their  faces  look 
happy  and  cheerful,  and  then  people  will  like 
to  be  with  them,  or  they  can  draw  the  muscles 
so  that  the  face  will  look  sour  and  cross,  and 
then  people  will  want  to  shun  them. 

We  must  be  careful  about  this  while  we  are 
young,  for  when  we  get  older  our  faces  will 
stay  the  way  we  have  trained  them. 

Now  hold  out  the  right  arm.  Place  the 
left  hand  upon  it  above  the  elbow.  Bring  the 
right  hand  up  towards  the  head,  and  you  can 
feel  a  large  muscle  which  gets  harder  and 
shorter.  This  is  the  one  that  bends  the  arm 
in  at  the  elbow. 


MUSCLES  31 

Put  the  left  hand  below  the  elbow  and  close 
the  fingers  of  the  ri^ht  hand.  You  can  easily 

o  o  J 

find  the  muscles  that  do  this  work. 

Now  grasp  the  back  of  the  leg  below  the 
knee  and  raise  yourself  upon  your  toes.  You 
find  here  a  large  muscle  which  pulls  hard 
enough  on  your  heel  to  raise  your  whole 
weight.  Every  movement  of  the  body  is 
made  by  a  muscle.  If  we  could  not  use  them 
we  would  be  perfectly  still  and  helpless. 

What  the  muscles  are. 

Most  of  the  meat  which  we  eat  is  muscle. 
Beefsteak  was  the  muscle  of  the  ox.  Lean 
pork  was  the  muscle  ot  the  hog.  When  these 
animals  were  alive  they  used  these  muscles  to 
move  themselves  about. 

When  you  get  a  piece  of  beefsteak  at  the 
butcher  shop  its  color  is  pink,  and  it  cannot 
be  easily  pulled  apart.  After  it  is  boiled  till 
it  is  tender,  you  can  divide  it  into  threads 
so  fine  that  you  can  hardly,  see  them.  A 
muscle  is  a  bundle  of  such  fine  threads  of 
lean  meat  tightly  bound  together. 

How  the  muscles  are  fastened  to  the  bones. 

Most  of  the  muscles  are  fastened  at  each 
end  to  a  bone.  When  they  get  shorter  they 


32 


FIRST   BOOK   OF   PHYSIOLOGY 


pull  on  the  bones,  and  in  that  way  we  make 
most  of  our  movements. 

Many  of  the  muscles  taper  at  the  ends  into 
a  white  cord,  and  this  cord  is  fastened  to  the 


10. — Tendons  of  hand. 


bone.  Rub  the  fingers  over  the  back  of  the 
hand  and  you  can  feel  the  cords  that  pull  the 
fingers  out  straight.  Try  it. 

It  would  not  do  to  have  large  muscles  down 


MUSCLES  33 

in  the  fingers  or  wrist,  for  that  would  make 
them  too  large  and  clumsy.  The  muscles 
that  close  and  open  the  fingers  are  put  on 
the  arm  below  the  elbow,  and  only  these 
tough,  slender  cords  run  down  to  the  fingers. 
In  this  way  the  hand  can  be  very  strong  and 
yet  be  small. 

Feel  across  the  inner  side  of  the  wrist. 
These  cords  pull  the  fingers  shut.  You  can 
see  them  in  picture  10. 

All  such  cords  are  called  tendons.  They  are 
used  in  a  number  of  places  in  the  body.  You 
can  easily  find  the  strong  tendons  at  the  elbow 
or  back  of  the  knee  or  back  of  the  ankle  above 
the  heel. 

How  we  make  our  muscles  work. 

The  muscles  cannot  move  themselves  any 
more  than  the  bones  can. 

How,  then,  can  you  throw  a  ball  or  run  or 
jump?  You  have  just  learned  that  all  the 
motions  of  the  body  are  made  by  the  mus- 
cles. You  can  sit  or  stand  whenever  you 
wish  to  do  so.  You  can  bend  your  arm  or 
knee  whenever  your  mind  tells  that  muscle 
to  go  to  work. 

The  mind  must  be  joined  to  the  muscle  in 
some  way. 

3 


34  FIRST   BOOK   OF    PHYSIOLOGY 

We  find  that  there  is  a  cord  called  a  nerve 
which  runs  from  the  brain  out  to  the  muscles. 

When  the  mind  wants  a  muscle  to  work,  it 
sends  word  down  along  the  nerve  and  the 
muscles  act  when  they  receive  this  order. 

We  will  learn  more  about  this  wonderful 
arrangement  when  we  get  farther  on  in  the 
book. 

In  picture  1 1  you  see  a  bundle  of  muscle. 
The  upper  part  shows  how  it  looks  when  it 


ii. — Muscle. 

is  resting.  When  the  mind  orders  it  to  go  to 
work,  it  draws  up  till  it  looks  like  the  lower 
part  of  the  picture.  By  doing  this  it  gets 
much  shorter  and  pulls  hard  on  anything  that 
is  fastened  to  the  end  of  it. 

We  have  some  muscles  that  do  their  work 
without  our  thinking  about  them.  Our  hearts 
work  all  day  and  at  night  while  we  are  asleep. 


MUSCLES  35 

The  muscles  that  make  us  breathe  keep  on 
working  while  we  are  thinking  about  other 
things.  If  we  had  to  think  of  our  heart  and 
lungs  to  keep  them  going,  we  would  not  have 
time  to  do  anything  else. 

How  to  make  muscle  strong  and  healthy. 

Muscles  get  strong  by  using  them.  If  you 
use  your  right  arm  more  than  the  left  one,  the 
right  arm  will  be  stronger.  When  a  muscle 
works  hard  more  blood  will  flow  to  it,  and  it 
will  keep  getting  larger  and  stronger. 

It  is  good  that  boys  and  girls  like  to  run 
and  jump  and  play  when  they  are  out  of 
doors.  This  gives  them  good  exercise  and 
makes  them  grow.  Play  is  not  the  only  exer- 
cise that  will  make  children  healthy.  Useful 
work  will  do  it  just  as  well.  Work  in  the 
garden  and  about  the  house  is  very  good 
exercise.  Any  outdoor  work  that  children 
do  cheerfully  is  good  for  their  health. 

Boys  sometimes  go  to  the  extreme,  and  try 
to  do  more  than  they  are  able  to  do.  Such 
exercise  does  more  harm  than  good.  You 
cannot  make  the  muscle  strong  by  working 
very  hard  for  a  few  days.  Good  exercise 
every  day  for  a  long  time  is  needed.  When 
you  are  very  tired  that  means  that  your 


36  FIRST   BOOK   OF    PHYSIOLOGY 

muscles  need  rest.  Good  air,  good  food, 
good  exercise,  and  the  proper  amount  of  sle<ip 
and  rest  will  give  you  healthy  and  strong 
muscles. 


Effect    of     cigarettes    and    tobacco    on     the 
muscles. 

It  is  certain  that  cigarettes  do  a  great  deal 
of  harm  to  the  muscles  as  well  as  to  the  whole 
body. 

A  boy  who  has  been  smoking  cigarettes  for 
some  time,  can  generally  be  picked  out  in 
school.  He  smells  bad,  to  begin  with  ;  but  that 
is  not  the  worst  part  of  it.  You  can  tell  from 
the  way  he  acts  that  there  is  something  wrong 
with  both  his  mind  and  his  body. 

It  has  been  found  in  many  schools  that  the 
boys  who  smoke  cigarettes  are  a  year  or  more 
behind  the  other  boys  who  do  not  smoke. 

Tobacco  is  a  poison  to  the  blood.  When 
the  blood  is  bad  no  part  of  the  body  can  be 
healthy. 

At  first  a  boy  gets  very  sick  when  he  tries 
to  use  tobacco.  All  tobacco  contains  a  deadly 
poison  called  nicotine.  It  is  this  poison  that 
makes  him  sick.  After  a  while  he  gets  used 
to  the  poison  and  it  will  not  make  him  sick, 
but  the  poison  harms  him  just  as  much. 


MUSCLES  37 

You  can  often  tell  that  a  boy  uses  tobacco 
by  the  way  he  works.  His  muscles  have 
been  poisoned  by  nicotine  or  have  been  starved 
by  bad  blood.  After  such  a  boy  works  for 
a  little  while  he  gets  very  tired.  A  healthy 
man  would  call  him  lazy,  but  he  does  get 
tired,  because  his  weak,  poisoned  muscle  does 
not  have  the  power  to  do  much  work. 

You  have  learned  that  the  muscles  are  all 
controlled  by  nerves.  Nicotine  also  poisons 
the  brain  and  nerves  so  that  they  cannot  send 
the  proper  order  down  to  the  muscles.  Such 
a  person  gets  awkward  and  his  hand  shakes. 
The  nerves  cannot  bring  the  right  kind  of 
an  order  to  the  muscles,  and  the  muscles  do 
not  have  the  strength  to  do  their  work. 

Effect  of  alcohol  on  the  muscles. 

There  are  some  drinks  that  are  very  bad 
for  the  muscles.  They  are  such  as  beer, 
whiskey,  wine,  and  hard  cider. 

These  drinks  are  not  good  for  us  because 
they  all  contain  alcohol.  Alcohol  is  a  poison 
to  the  body. 

People  used  to  think  that  alcohol  made  the 
muscles  stronger.  They  thought  they  could 
do  more  work  when  they  drank  whiskey  and 
beer.  We  know  now  that  this  is  not  true.  It 


38  FIRST   BOOK   OF   PHYSIOLOGY 

has  been  tried  many  times,  and  it  is  always 
found  that  the  men  who  drink  whiskey  aild 
beer  and  wine  will  get  tired  and  give  out 
sooner  than  those  who  do  not. 

The  young  men  who  are  trained  for  hard 
games,  like  boat-racing,  foot-ball,  wrestling, 
and  the  like,  are  not  allowed  to  use  any  alco- 
hol or  tobacco.  The  muscle  cannot  be  trained 
to  work  hard  for  a  long  time  if  it  has  any 
nicotine  or  alcohol  in  it. 

Some  people  think  they  can  make  them- 
selves healthy  by  drinking  beer,  because  beer 
makes  them  fat.  They  think  they  are  healthy 
when  the  body  is  fat.  This  is  a  great  mistake. 
They  get  more  fat,  but  less  muscle.  They 
get  weak  instead  of  strong.  Our  strength  is 
in  our  muscles,  and  not  in  our  fat. 

You  can  plainly  see  why  men  and  boys  who 
drink  alcohol  and  smoke  cigarettes  are  not 
wanted  in  the  stores,  or  in  the  shops,  or  on  the 
railroads.  They  are  not  worth  as  much  as 
are  those  with  strong,  healthy  bodies. 

The  only  safe  way  is  to  let  tobacco  and 
strong  drink  alone. 

Your  body  is  doing  its  best  all  the  time  to 
keep  you  in  good  health.  You  ought  to  help 
it,  and  not  hinder  it. 


MUSCLES  39 

Questions. 

1.  Name  four  uses  of  bones. 

2.  How  can  the  bones  be  made  to  move  ? 

3.  Find  the  muscle  you  use  when  you  bring  your  hand  to 
your  mouth. 

4.  What  is  a  muscle  ? 

5.  How  are  muscles  fastened  to  bones  ? 

6.  What  are  tendons  ?     Where  can    you   find  some  of 
them? 

7.  How  can  the  mind  make  the  muscle  work  ? 

8.  How  can  a  muscle  move  a  bone  ? 

9.  Name  some  muscles  that  keep  working  all  the  time. 

10.  What  will  exercise  do  for  the  muscles  ? 

1 1 .  What  are  some  of  the  bad  effects  of  smoking  ciga- 
rettes ? 

12.  Why  is  a  cigarette  smoker  not  wanted  in  the  big  stores 
and  shops  ? 

13.  What  are  some  of  the  bad  results  of  drinking  alcohol  ? 

14.  What  is  the  best  drink  ? 


CHAPTER-IV 

FOOD 

Appetite. 

THE  growing  boy  or  girl  gets  hungry  very 
often.  This  is  the  way  our  bodies  tell  us  that 
we  need  more  food. 

If  you  are  healthy  and  do  not  spoil  your 
appetite,  it  will  tell  you  just  what  you  ought 
to  eat.  Sometimes  it  tells  us  to  eat  some- 
thing sour.  At  other  times  it  tells  us  to  eat 
something  sweet.  Sometimes  it  will  call  for 
vegetables,  and  at  other  times  for  meat. 

When  we  are  sick  our  appetites  often  call 
for  things  that  are  not  good  for  us.  At  such 
times  we  must  eat  only  what  the  doctor  tells 
us  to  eat. 

Some  boys  spoil  their  appetites  by  doing 
things  that  make  the  body  unhealthy.  The 
boy  who  uses  tobacco  will  get  an  appetite  for 
it  that  will  grow  stronger  and  stronger.  It  is 
not  safe  for  him  then  to  follow  his  appetite 
in  anything. 

People  who  drink  whiskey  or  beer  or  any 

strong  drink  that  has  alcohol  in  it  will  get  a 
40 


FOOD  41 

very  strong  appetite  for  such  drinks.  The 
more  they  drink  the  stronger  the  appetite 
becomes. 

After  a  while  the  appetite  gets  stronger 
than  the  man,  and  he  cannot  quit  even  when 
he  wants  to  do  so. 

A  good  appetite  will  always  want  the 
things  that  are  good  for  us. 

Sometimes  even  young  boys  and  girls  lose 
their  appetites.  They  come  to  the  table  at 
meal-time,  but  cannot  find  anything  there  that 
they  like.  This  means  that  something  is 
wrong.  Maybe  they  have  been  eating  too 
much  candy  or  other  things  between  meals. 
Maybe  they  ate  too  much  at  the  last  meal  or 
have  not  had  enough  exercise. 

Here  is  a  good  recipe  for  keeping  up  a 
healthy  appetite.  It  was  written  by  Alice 


Gary. 


"  My  lad,  who  sits  at  breakfast 
With  forehead  in  a  frown 
Because  the  chop  is  under-done 
And  the  fritter  over-brown, 


Just  leave  your  dainty  mincing 
And  take,  to  mend  your  fare, 

A  slice  of  golden  sunshine 
And  a  cup  of  morning  air. 


42  FIRST   BOOK   OF   PHYSIOLOGY 

' '  And  when  you  have  eat  and  drunken, 

If  you  want  a  little  fun, 
Throw  by  your  jacket  of  broadcloth 
And  take  an  up-hill  run. 

"  And  with  the  one  and  the  other 
You  will  be  so  strong  and  gay 
That  work  will  be  only  a  pleasure 
Through  all  the  rest  of  the  day. 

"  And  when  it  is  time  for  supper 
Your  bread  and  milk  will  be 
As  sweet  as  a  comb  of  honey. 
Will  you  try  -my  recipe  ?' ' 

Why  we  eat. 

Our  food  does  three  things  for  us.  It 
makes  us  grow.  It  makes  us  warm.  It  makes 
us  strong,  so  that  we  can  work. 

We  can  say  that  a  steam-engine  eats  coal. 
The  engine  will  run  as  long  as  the  engineer 
keeps  up  a  good  fire  and  keeps  water  in  the 
boiler.  When  he  lets  the  fire  go  down  the 
engine  will  stop.  Then  we  can  say  that  the 
engine  is  hungry  and  must  have  some  more 
of  its  kind  of  food  before  it  will  run  again. 

When  you  get  tired  and  hungry,  you  know 
that  you  must  eat  again  before  you  can  do 
much  more  work.  We  eat  for  nearly  the 
same  reason  the  engine  does,  but  we  cannot 
use  coal  for  our  food. 


FOOD  43 

The  proper  kinds  of  food  for  us. 

We  need  five  different  kinds  of  food. 

The  first  kind  is  proteid.  We  get  it  from 
such  food  as  eggs,  meat,  vegetables,  and 
milk. 

The  second  kind  is  starch.  We  get  it  from 
such  food  as  flour,  rice,  potatoes,  and  fruit. 

The  third  kind  \sfat.  We  get  it  from  such 
food  as  butter,  cream,  and  fat  meat. 

The  fourth  kind  is  water. 

The  fifth  kind  is  the  minerals. 

No  one  of  these  kinds  of  food  would  sat- 
isfy us.  We  must  have  some  of  each  kind. 
Milk  is  nearly  a  perfect  food,  for  it  has  all 
the  different  kinds  mixed  together. 

Tea  and  coffee  are  not  foods  at  all.  Chil- 
dren will  always  be  in  better  health  if  they 
drink  only  milk  and  water.  They  should 
never  drink  tea  and  coffee. 

Enough  of  all  the  minerals,  except  one,  is 
already  in  the  other  kinds  of  food.  That  one 
is  salt.  So  we  add  salt  to  our  food  when  we 
cook  it  or  while  we  are  eating. 

Water. 

A  large  part  of  the  body  is  water. 

We  cannot  live  long  without  it.     All  of  our 


44  FIRST   BOOK   OF   PHYSIOLOGY 

foods  contain  water,  but  we  need  to  drink  a 
great  deal  besides. 

Water  is  a  food  because  our^bodies  need  it 
and  cannot  be  healthy  without  it. 

It  is  our  natural  drink,  and  when  we  are 
real  thirsty  nothing  is  so  good. 

It  is  a  blessing  that  water  is  so  plentiful. 
Some  places  are  a  desert  because  there  is  no 
water  there,  but  we  have  great  lakes  and 
rivers  of  it.  We  can  drill  a  hole  down  into 
the  ground  and  are  almost  sure  to  strike  a 
vein  of  good,  fresh  water.  Sometimes  it 
comes  up  itself  to  the  top  of  the  ground  in  a 
cool  spring. 

The  water  that  comes  from  springs  or  from 
deep  wells  is  nearly  always  good  to  drink. 
The  water  from  a  shallow  well  or  from  a  river 
near  a  town  or  city  may  be  very  bad.  A 
great  deal  of  sickness  and  death  is  caused  by 
drinking  impure  water.  If  you  think  the 
water  you  have  to  drink  is  not  good,  you 
should  boil  it  before  you  drink  it. 

Never  drink  the  water  from  a  shallow  well 
if  you  can  avoid  it.  Here  you  see  the  top  of 
a  well  which  is  almost  sure  to  contain  bad 
water.  The  well  is  walled  up  with  loose 
stones  and  is  only  about  fifteen  feet  deep. 
When  a  heavy  rain  falls,  the  water  will  carry 


FOOD  45 

into  this  well  any  poison  or  filth  that  may  be 
near.  The  well  may  look  clean  and  neat  on 
top  and  yet  hold  very  bad  water.  Whole 
families  often  get  typhoid  fever  or  other  kinds 
of  disease  by  drinking  from  such  a  well. 


12. — An  old  well. 

The  ice  which  is  used  in  the  summer-time 
should  never  be  put  into  the  drinking-water. 
The  ice  is  not  pure  when  it  is  taken  off  of 
water  that  was  impure.  Then,  too,  the  ice  in 
the  water  makes  it  too  cold  to  drink.  It  is 


46  FIRST   BOOK    OF    PHYSIOLOGY 

much  better  to  drink  the  water  just  as  it 
comes  from  the  hydrant  or  spring  or  dt&p 
well. 

Manners  at  the  table. 

There  is  a  right  and  a  wrong  way  to  act 
while  you  are  at  the  table.  It  is  easy  to  tell 
how  boys  and  girls  have  been  trained  by  see- 
ing how  they  eat. 

Everything  that  is  done  at  the  table  should 
be  refined  and  polite. 

We  cannot  tell  you  here  all  the  things  you 
should  do  or  should  not  do  at  the  table,  but 
here  are  a  few  rules  which  you  must  try  to 
observe. 

Be  sure  you  never  use  a  knife  to  carry  the 
food  to  your  mouth.  You  must  use  your 
fork  or  spoon  for  that  purpose  and  must 
learn  the  right  way  to  hold  them. 

Be  careful  not  to  make  any  noise  with  your 
mouth  when  you  eat  or  drink. 

Do  not  let  your  knife  or  fork  rattle  on  your 
plate. 

Do  not  lounge  or  rest  your  elbows  upon 
the  table. 

Do  not  rise  in  your  chair  to  reach  for  any- 
thing. Ask  for  it  in  a  polite  way. 

While  we  eat  we  should  be  cheerful  and 


FOOD  47 

happy.  This  will  not  only  give  us  a  pleas- 
ant time,  but  our  food  will  do  us  more 
good. 

There  are  many  rules  of  this  kind,  and  you 
can  soon  learn  them  if  you  will  try. 

Your  teacher  will  tell  you  about  them,  and 
you  can  notice  how  polite  people  eat. 

Every  one  will  be  much  better  pleased  with 
you  when  you  eat  in  the  right  way,  and  you 
will  not  need  to  be  ashamed  to  eat  with  polite 
people  when  you  are  older. 

Questions. 

1 .  What  does  the  appetite  tell  us  ? 

2.  How  may  the  appetite  be  spoiled? 

3.  Repeat  Alice  Gary's  recipe  for  an  appetite. 

4.  Why  do  we  eat  ? 

5.  What  three  things  will  food  do  for  us  ? 

6.  What  kinds  of  food  do  we  need  ? 

7.  What  are  the  best  drinks  ? 

8.  Where  can  pure  water  be  found  ? 

9.  Why  do  shallow  wells  often  contain  impure  water  ? 

10.  Why  is  it  wrong  to  drink  ice-water  ? 

11.  Why  should  we  be  cheerful  and  happy  at  the  table  ? 

12.  Tell  all  you  can  about  good  and  bad  table  manners. 


CHAPTER    V 

DIGESTION 

The  teeth. 

After  the  food  is  taken  into  the  mouth  it 
must  be  chewed.  This  is  done  by  the  teeth. 
You  had  no  teeth  till  you  were  a  little  over 
a  year  old,  and  then  your  first  set  came 
through  the  gums.  Then  you  had  only  ten 
upper  teeth  and  ten  lower  ones. 

When  you  were  six  or  seven  years  old 
your  first  teeth  came  out  and  new  ones  came 
in  their  places.  Count  your  teeth  and  see 
how  many  you  have  now. 

These  are  the  only  teeth  you  will  ever  have, 
and  if  you  take  good  care  of  them  they  will 
last  a  longf  time. 

o 

How  a  tooth  looks  on  the  inside. 

Picture  13  shows  you  how  a  tooth  looks 
when  it  is  cut  in  two  lengthwise.  A  tooth  is 
alive  and  grows  like  other  parts  of  the  body. 
It  gets  its  food  from  the  blood.  At  the  lower 
end  of  the  tooth  you  can  see  how  the  blood- 
tubes  enter  and  carry  blood  up  through  the 

centre. 
48 


DIGESTION  49 

In  the  picture  you  see  that  in  this  tooth 
eight  lines  enter  in  at  the  bottom.  Six  of 
them  stand  for  blood-tubes  and  two  of  them 
for  nerves.  These  nerves  also  run  to  all  parts 
of  this  central  part  of  the  tooth.  Even  a  very 
small  opening  in  to  where  the  nerves  are  will 
give  us  a  severe  toothache. 


13. — Section  of  front  tooth. 

The  outside  rim  at  the  top  of  the  tooth  is 
called  enamel.  It  is  the  hardest  substance  in 
the  whole  body.  When  the  enamel  is  kept 
clean  it  is  a  beautiful  white,  and  needs  to  be 
very  hard,  for  we  use  it  to  grind  our  food. 

Care  of  teeth. 

The  teeth  are  not  only  useful  for  chewing 
our  food,  but  we  look  much  better  when  we 
have  sound  white  teeth. 

4 


5o  FIRST  BOOK   OF   PHYSIOLOGY 

The  girl  in  the  picture  is  enjoying  a  hearty 
laugh.  It  does  any  one  good  to  have  a  hearty 
laugh  when  something  very  amusing  happens. 
At  such  times  a  set  of  sound  white  teeth, 


14. — A  girl  laughing. 

such  as  this  girl  has,  adds  very  much  to  the 
personal  appearance. 

The  best  way  to  have  good  teeth  is  to  be- 
gin to  take  care  of  them  when  we  first  get 
them. 

Here  are  a  few  rules  that  you  ought  to 
follow. 

Never  pick  your  teeth  with  a  pin  or  any 
other  hard  substance.  Use  a  toothpick. 


DIGESTION 


51 


Do  not  bite  on  anything  that  is  hard. 

Do  not  allow  any  bits  of  food  or  candy  to 
remain  between  the  teeth. 

Wash  the  teeth  often  with  a  tooth-brush. 

Do  not  take  any  very  hot  or  very  cold 
liquid  into  the  mouth.  Either  may  crack  the 
enamel. 

Have  the  dentist  look  over  your  teeth  once 
in  a  while  to  see  if  they  are  sound.  A  small 
cavity  can  be  filled  with  gold  and  the  tooth 
will  be  almost  as  good  as  new. 

Saliva. 

When  you  think  of  something  real  good  to 
eat  you  say  it  makes  your  mouth  water.  This 
fluid  is  called  saliva.  While  we  are  grinding 
our  food  between  our  teeth  a  great  deal  of 
saliva  pours  into  the  mouth.  It  wets  the  food 
and  changes  some  of  the  bread  and  potatoes 
and  other  kinds  of  starch  into  sugar. 

When  the  food  has  been  ground  up  fine 
and  mixed  with  the  saliva  the  tongue  pushes 
it  into  the  back  part  of  the  mouth. 

Swallowing. 

The  food  is  now  ready  to  be  swallowed.  It 
enters  the  top  of  a  tube  called  the  gullet  or 
oesophagus.  The  gullet  is  just  back  of  the 


52  FIRST   BOOK   OF    PHYSIOLOGY 

windpipe.  The  muscles  of  this  tube  squeeze 
the  food  down  farther  and  farther  till  it  reaches 
the  stomach.  This  is  done  every  time  we 
swallow. 

If  we  attempt  to  swallow  food  that  has  not 
been  well  chewed  and  mixed  with  saliva  it  will 
stick  in  the  gullet.  The  same  thing  will  hap- 
pen if  we  try  to  swallow  too  large  a  mouthful. 
Some  animals  have  been  choked  to  death  in 
this  way. 

The  large  lump  of  food  that  is  stuck  in  the 
gullet  will  press  on  the  back  part  of  the  wind- 
pipe and  shut  off  our  breath. 

The  stomach. 

The  stomach  is  a  bag  that  looks  very  much 
like  what  you  see  at  the  top  of  this  picture. 
A  man's  stomach  will  hold  about  three  pints. 
The  gullet  pushes  the  food  in  at  the  top. 
Then  the  muscles  of  the  stomach  begin  to 
roll  the  food  about  and  mix  it  thoroughly. 

At  the  same  time  the  stomach  pours  out  on 
the  food  a  sour  liquid  called  the  gastric  juice. 
This  juice  will  digest  nearly  all  of  the  first  kind 
of  foods  that  we  told  you  about  on  page  43. 
It  changes  such  food  to  a  liquid  form. 

You  can  now  see  why  the  food  should  be 
cooked  till  it  is  tender  and  then  chewed  real 


DIGESTION  53 

fine  before  it  is  swallowed.     The  stomach  can 
then  easily  mix  it  with  the  gastric  juice. 

As  soon  as  any  of  the  food  is  digested  and 
changed  to  a  liquid  it  passes  out  at  the  other 
end  of  the  stomach. 


15. — Stomach  and  intestines. 

After  a  hearty  meal  it  will  be  two  or  three 
hours  before  the  stomach  is  empty  again.  If 
the  stomach  is  not  healthy  or  the  food  is  very 
hard  to  digest  it  may  take  four  hours  or  more. 


54  FIRST   BOOK   OF   PHYSIOLOGY 

After  the  stomach  has  been  hard  at  wor-k 
with  one  meal,  it  should  be  allowed  to  rest  for 
a  while.  It  is  a  bad  practice  to  eat  between 
meals.  Wait  till  the  next  regular  meal,  and 
then  the  stomach  will  be  greedy  to  get  it  and 
digest  it  for  you. 

Many  people  eat  too  much.  They  keep  on 
eating  even  after  they  know  they  have  enough. 
They  fill  the  stomach  so  full  that  it  cannot 
work  well.  There  is  not  enough  gastric  juice 
to  digest  so  much  food  at  once.  This  is  not 
so  bad  when  we  are  eating  simple  food  like 
corn  bread  or  potatoes  or  oat-meal,  but  it 
is  very  bad  for  us  when  we  eat  too  much 
of  the  strong  foods  like  pork  and  beef  and 
eggs. 

You  should  quit  eating  just  as  soon  as  you 
begin  to  feel  satisfied.  It  is  not  the  amount 
we  eat  that  does  us  good,  but  the  amount  we 
can  digest  and  use. 

Any  food  more  than  this  is  only  a  burden 
to  the  body,  and  is  sure  to  produce  poisons 
that  will  make  us  sick. 

The  intestines. 

When  the  food  leaves  the  stomach  it  passes 
into  a  long  tube  called  the  intestines.  In  the 
picture  15  you  see  them  below  the  stomach. 


DIGESTION  55 

They  are  often  called  the  bowels.  You  see 
there  are  two  kinds.  The  small  intestines  are 
in  the  centre  and  the  large  ones  are  around 
them.  This  tube  is  very  soft  and  is  folded 
back  and  forth  many  times.  If  it  were 
stretched  out  into  a  straight  tube  it  would 
reach  a  distance  of  nearly  twenty  feet. 

When  the  food  gets  into  the  small  intestine 
two  more  juices  are  poured  out  upon  it. 

Bile. 

One  of  these  juices  is  called  bile.  The  bile 
is  made  by  the  liver,  which  is  on  your  right 
side  just  under  the  lowest  ribs.  The  liver 
stores  the  bile  in  a  little  bag  called  the  gall- 
bladder. When  the  food  comes  along,  this 
juice  pours  out  onto  it  and  helps  a  great  deal 
in  digestion. 

Pancreatic  juice. 

The  other  juice  is  called  the  pancreatic  juice. 
It  is  gathered  up  by  the  pancreas,  which  lies 
right  below  the  stomach,  and  is  not  nearly  so 
large  as  the  liver.  This  juice  is  poured  out 
onto  the  food  along  with  the  bile,  and  the  two 
work  together  to  digest  the  food  in  the  intes- 
tines. 


56  FIRST   BOOK  OF   PHYSIOLOGY 

How  the  food  gets  into  the  blood. 

The  bile  and  the  pancreatic  juice  digest  the 
food  that  was  not  digested  before.  No  food 
can  get  into  the  blood  or  do  us  any  good  until 
it  is  first  changed  to  a  liquid.  The  muscles 
of  the  intestines  keep  mixing  the  food  with 
these  juices  till  it  is  all  in  a  liquid  form.  Then 
it  soaks  through  the  sides  of  the  intestines  and 


1 6. — Section  of  small  intestine. 

is  carried  away  in  the  blood-tubes.  In  picture 
1 6  you  see  a  very  thin  slice  across  the  small 
intestine  of  a  cat.  It  is  enlarged  here  so  you 
can  see  it  more  plainly.  Ours  are  made  in  the 
same  way.  You  see  the  tube  is  not  smooth 
on  the  inside,  but  is  much  like  the  nap  on 
velvet.  Each  little  tuft  has  blood-tubes  in  it, 


DIGESTION 


57 


and  when  the  food  comes  along  it   is    easily 
soaked  up  and  carried  away  in  the  blood. 

Picture   1 7  shows  you  how  some  of  these 
same  tufts  look  when  we  see  them  through  a 


17. — Villi  of  small  intestine. 

strong  microscope.  You  can  see  the  blood- 
tubes  running  down  into  each  one  and  coming 
close  to  the  food. 

The  work  of  the  liver. 

After  the  food  gets  out  of  the  intestine  and 
into  the  blood-tubes  it  is  not  yet  ready  to  be 
sent  out  over  the  body..  It  is  not  good  blood 
yet.  Nearly  all  of  it  must  now  go  through 
the  liver.  The  liver,  as  we  have  learned, 
takes  bile  out  of  it.  It  also  takes  out  other 
things  that  would  poison  us  if  they  would  ever 


58  FIRST   BOOK   OF   PHYSIOLOGY 

get  to  the  heart.  It  changes  the  food,  too,  in 
some  other  ways. 

After  the  liver  has  done  its  part,  the  liquid 
food  is  now  ready  to  be  carried  up  to  the 
heart. 

A  good  liver  is  our  most  faithful  friend.  If 
it  gets  out  of  order,  everything  goes  wrong, 
and  we  become  very  sick. 

Review  of  the  work  of  digestion. 

After  you  swallowed  your  food  you  did  not 
have  to  give  it  any  further  attention. 

The  stomach  took  whatever  you  gave  it, 
and  poured  upon  it  the  sour  gastric  juice  and 
mixed  all  well  together.  This  digested  part 
of  the  food  and  it  began  to  flow  out  of  the 
other  end  of  the  stomach  into  the  small  in- 
testine. In  three  or  four  hours  the  stomach 
was  empty. 

In  the  intestines  two  more  juices  were 
poured  upon  the  food.  They  are  called  the 
bile  and  the  pancreatic  juice.  The  bile  is 
made  by  the  liver  and  the  pancreatic  juice  is 
made  by  the  pancreas.  The  intestines  mixed 
the  food  with  these  juices  and  digested  all 
that  was  not  digested  in  the  stomach. 

Now  the  food  was  all  in  a  liquid  form,  and 
soaked  through  the  sides  of  the  intestine  and 


DIGESTION  59 

was  carried  away  in  blood-tubes  to  the  liver. 
The  liver  purified  it  and  made  it  into  the 
right  kind  of  blood  for  the  body,  and  then  it 
was  sent  on  to  the  heart. 

This  is  all  wonderful,  and  you  will  learn 
many  more  interesting  things  about  it  in  the 
larger  books. 

Care  of  stomach  and  intestines. 

Every  boy  and  girl  wants  to  have  a  healthy 
stomach  and  intestines. 

People  who  have  stomach  trouble  are  very 
miserable,  and  are  of  little  use  in  any  kind  of 
work  until  they  get  well  again.  If  your  stom- 
ach and  intestines  will  not  do  their  work,  it  is 
no  use  for  you  to  eat.  The  food  cannot  do 
you  any  good,  for  it  cannot  be  digested  and 
get  into  the  blood. 

The  way  to  keep  anything  in  good  order  is 
to  take  good  care  of  it.  Learn  to  do  this 
while  you  are  young,  and  you  will  be  sure  to 
have  better  health  and  will  be  much  happier 
when  you  are  older. 

Here  are  some  things  that  you  should  do 
and  some  things  you  should  not  do.  Follow 
all  of  these  rules,  and  you  will  never  be 
troubled  with  bad  digestion  : 

Eat  only  good  food. 


60  FIRST  BOOK   OF   PHYSIOLOGY 

Eat  food  that  is  well  cooked. 

Chew  the  food  thoroughly  till  it  is  in  fine 
pieces. 

Drink  only  milk  and  water. 

Eat  only  three  times  a  day.  The  stomach 
must  have  some  rest. 

Stop  eating  before  the  stomach  is  too  full. 
Overeating  is  the  cause  of  a  great  deal  of 
trouble. 

Eat  but  little  candy,  and  have  it  pure. 

Never  drink  ice-water.  The  water  may  be 
cool,  but  ice-cold  water  is  always  bad  for  the 
stomach.  If  you  want  to  cool  off,  plunge  your 
hands  into  cold  water,  but  do  not  drink  it. 

Be  cheerful  and  happy  while  you  eat. 
Good  cheer  will  help  digestion. 

Never  drink  anything  that  has  alcohol  in  it, 
for  alcohol  spoils  the  gastric  juice  and  makes 
the  food  hard  to  digest. 

Do  not  drink  anything  while  the  mouth  is 
full  of  food.  Keep  on  chewing  the  food  till 
the  saliva  has  had  time  to  wet  it.  Food 
digests  better  when  it  is  well  mixed  with 
saliva. 

Eat  more  of  the  simple,  coarse  foods  and 
less  of  the  strong  meats.  A  good  soup  made 
of  beef-broth  and  vegetables  is  an  excellent 
food. 


DIGESTION  61 

A  story. 

A  long  time  ago  there  was  a  great  king 
whose  name  was  Nebuchadnezzar.  He  lived 
in  a  grand  palace  and  had  an  army  of  ser- 
vants about  him  to  do  his  bidding.  One  day 
he  told  his  chief  servant  to  search  through  his 
kingdom  for  the  best  boys  he  could  find  and 
bring  them  to  the  palace. 

The  king  told  him  to  get  only  those  boys 
who  had  good  health  and  a  pleasing  face 
and  who  were  quick  to  learn.  The  servant 
hunted  all  around  and  brought  in  a  large 
number  of  the  best  boys. 

Then  the  king  told  him  to  take  good  care 
of  them  and  train  them  for  three  years.  At 
the  end  of  that  time  the  king  said  he  would 
call  the  boys  before  him,  so  that  he  could  see 
how  they  looked  and  what  they  could  do. 

Now  the  king  had  told  his  servant  to  give 
the  boys  all  the  rich  food  they  could  eat. 
They  could  have  all  the  meats  and  dainties 
they  wanted  and  all  the  wine  they  could 
drink.  Their  table  was  to  be  just  as  rich  as 
that  of  the  king  himself.  He  thought  he  was 
doing  the  best  thing  for  the  boys. 

The  most  of  them  ate  and  drank  what  the 
servant  gave  them,  and  thought  it  was  very 
good  ;  but  four  of  them  did  not  like  this  rich 


62  FIRST   BOOK    OF    PHYSIOLOGY 

food,  and  asked  the  servant  to  let  them  have 
just  simple  vegetable  soup,  and  instead  of 
wine  they  asked  for  pure  water. 

Then  the  servant  said  that  he  had  to  do  just 
as  the  king  told  him,  and  he  feared  his  master 
would  be  angry  unless  they  did  just  as  they 
were  ordered  to  do. 

The  four  boys  then  asked  him  to  try  them 
just  for  ten  days  to  see  how  they  would  get 
along,  and  not  tell  the  king  anything  about 
it.  They  knew  that  they  were  right. 

The  servant  liked  these  boys,  and  so  he  let 
them  try  it.  When  the  ten  days  were  up,  they 
looked  so  healthy  and  were  so  bright  that  the 
servant  let  them  eat  this  kind  of  food  all  the 
time. 

At  the  end  of  the  three  years  the  king-  sent 
for  all  the  boys.  He  looked  at  them  closely 
and  examined  them  to  see  what  they  could  do. 
Then  he  picked  out  these  four  boys  because 
they  had  the  best  health  and  the  brightest 
minds,  and  he  kept  them  in  his  palace. 

They  were  a  great  help  to  the  king,  and 
grew  up  to  be  very  famous  men.  We  often 
talk  and  read  about  them  even  to  the  present 
day. 


DIGESTION  63 

Questions. 

1.  How  many  teeth  have  you  in  each  jaw  ? 

2.  What  causes  tooth-ache  ? 

3.  Why  is  the  enamel  on  a  tooth  so  hard  ? 

4.  Why  should  we  take  care  of  our  teeth  ? 

5.  How  can  we  care  for  our  teeth  ? 

6.  What  is  saliva,  and  of  what  use  is  it  ? 

7.  Tell  what  you  know  about  swallowing. 

8.  Describe  the  stomach. 

9.  What  does  the  stomach  do  with  the  food  ? 

10.  Why  is  it  wrong  to  eat  too  much  or  to  eat  between 
meals  ? 

11.  What  two  juices  act  on  the  food  in  the  small  intestine  ? 

12.  Tell  about  bile. 

13.  Tell  about  pancreatic  juice. 

14.  Why  must  food  be  digested  ? 

15.  How  does  the  food  get  into  the  blood  ? 

1 6.  Tell  what  you  can  about  the  work  of  the  liver. 

17.  Give  a  short  account  of  the  whole  work  of  digestion. 

1 8.  Give  some  rules  for  eating  and  drinking. 

19.  Tell  the  story  of  the  four  boys. 

20.  What  were  the  names  of  these  boys  ? 


CHAPTER    VI 

THE    BLOOD 

THE  blood  goes  to  every  part  of  the  body. 
It  makes  its  way  even  into  the  hard  bone  and 
the  teeth.  If  you  push  a  fine  needle  through 
the  skin  at  any  place  on  the  body,  some  blood 
will  run  out.  The  skin  looks  pink  and  the 
cheeks  red  because  the  red  blood  is  just  under 
the  skin. 

There  is  enough  blood  in  your  body  to  fill 
a  tincup  six  or  eight  times.  Of  course,  there 
is  more  blood  in  a  large  body.  A  large  man 
has  about  eight  quarts  of  blood. 

About  one-thirteenth  of  the  weight  of  the 
body  is  blood.  If  your  weight  is  one  hundred 
and  thirty  pounds,  then  your  blood  by  itself 
would  weigh  ten  pounds.  Divide  your  weight 
in  pounds  by  thirteen,  and  the  answer  will  be 
about  the  number  of  pounds  of  blood  you 
have. 

The  heart. 

The    blood    is    never    still.       It   is    moving 
around  and  around  through  the  body  all  the 
64 


THE   BLOOD  65 

time.     What  makes  it  move?     You  say  the 
heart  does  it,  and  that  is  correct. 

In  the  picture  you  see  how  the  heart  looks. 
It  is  about  as  large  as  the  fist  and  is  made  of 
strong  muscles.  The  heart  is  double.  There 
is  the  right  heart  and  the  left  heart.  These 
two  are  tightly  fastened  together.  The  left 
heart  is  stronger  than  the  right  one  because 
it  has  harder  work  to  do.  Each  half  of  the 


1 8. —The  heart. 

heart  has  two  tubes  at  the  top  of  it.  One 
tube  carries  the  blood  in  and  the  other  carries 
it  out.  The  blood  first  goes  into  the  right 
heart,  and  when  it  is  full  it  squeezes  upon  the 
blood  and  forces  it  out  through  the  other  tube 
and  sends  it  to  the  lungs. 

When  it  comes  back  from  the  lungs  it  goes 
into  the  left  heart,  and  when  it  is  full  the 
strong  muscles  on  that  side  squeeze  the  blood 

5 


66  FIRST   BOOK   OF   PHYSIOLOGY 

out   through    another    tube   and   send   it  out 
on  its  trip  through  the  whole  body. 

Care  of  the  heart. 

You  all  know  where  your  heart  is,  but  may- 
be you  have  not  thought  how  faithful  it  is  to 
you.  It  beats  all  day  and  all  night.  The  only 
rest  it  ever  gets  is  the  short  time  between  the 
beats.  If  your  heart  would  get  badly  out  of 
order  or  would  stop  for  just  one  minute  you 
would  die. 

Some  people  take  very  poor  care  of  the 
heart.  Boys  and  men  often  have  what  the 
doctor  calls  "tobacco  heart."  Such  a  heart 
will  flutter.  At  times  it  beats  very  rapidly 
and  at  other  times  slowly. 

This  bad  condition  is  often  caused  by 
smoking  cigarettes  or  by  using  tobacco  in  any 
way.  If  the  heart  does  not  beat  as  it  should, 
then  the  body  cannot  get  the  blood  it  needs. 
You  cannot  be  healthy  without  a  good  heart. 
Your  heart  will  do  good  work  for  you  if  you 
do  not  hinder  it. 

Beer  is  bad  for  the  heart,  for  beer  makes 
fat.  The  heart  must  be  made  of  strong  mus- 
cles. Beer  changes  some  of  the  muscles  of 
the  heart  to  fat.  This  makes  the  heart  weak, 
and  it  is  not  able  to  send  out  a  strong  current 


THE   BLOOD  67 

of  blood  through  the  body.  People  often  die 
because  they  keep  on  drinking  beer  till  the 
heart  is  so  fat  and  weak  that  it  cannot  work 
any  longer. 

The  arteries. 

The  blood  is  forced  out  by  the  heart 
through  strong  tubes  called  arteries.  They 
spread  out  all  over  the  body.  They  divide 
into  a  great  many  branches,  and  get  smaller 
and  smaller  till  they  are  finer  than  a  hair. 
When  an  artery  is  cut  the  blood  will  spurt 
out  in  a  stream.  If  the  artery  is  a  large  one, 
the  person  would  soon  bleed  to  death  unless 
he  knew  what  to  do  at  once.  If  such  an  acci- 
dent should  ever  happen  to  you  or  to  one  of 
your  friends,  press  the  cut  tight  together  with 
both  hands.  Do  not  be  afraid  of  the  blood. 
No  time  must  be  lost. 

Also,  if  you  can  have  some  one  to  help,  tie 
a  handkerchief  or  strong  cord  around  the  leg 
or  arm  above  the  cut.  Draw  the  cord  as  tight 
as  you  can  to  press  the  artery  shut,  so  the 
blood  cannot  get  down  to  the  cut.  As  soon 
as  the  doctor  comes  he  will  know  what  to  do. 

The  pulse. 

The  arteries  are  put  deep  down  under  the 
skin,  but  in  a  few  places  they  come  very 


68  FIRST   BOOK   OF    PHYSIOLOGY 

close  to  the  surface.  At  such  places  we  can 
plainly  feel  the  pressure  on  the  blood  when- 
ever the  heart  beats.  This  pressure  or  throb- 
bing in  an  artery  is  called  the  pulse. 

The  pulse  can  be  felt  most  plainly  at  the 
wrist. 

The  girl  in  the  picture  is  counting  her 
pulse.  If  she  does  it  correctly,  she  will  know 
how  fast  her  heart  is  beating.  You  try  it. 


19. — Counting  the  pulse. 

Look  at  the  second-hand  of  a  watch  and 
count  till  it  goes  once  around.  This  tells  you 
how  often  your  heart  beats  in  one  minute. 

I  have  just  tried,  and  I  find  that  my  heart  is 
beating  eighty  times  in  one  minute. 


THE    BLOOD  69 

How  fast  does  yours  beat  ? 

Now  exercise  for  a  few  minutes  and  then 
count  again.  See  how  much  faster  the  heart 
is  beating.  When  we  work  we  need  more 
blood.  The  heart  tries  to  give  it  to  us. 
What  a  faithful  old  heart  we  have  ! 

Capillaries. 

At  the  ends  of  the  arteries  is  a  network  of 
very  fine  tubes  called  capillaries. 

The  blood  is  now  pushed  on  from  the  ar- 
teries into  these  small  tubes.  Here  is  where 
the  blood  feeds  the  body  and  takes  away  any 
waste  matter.  The  capillaries  are  very  small, 
short  tubes  ;  but  there  are  so  many  of  them 
that  if  you  push  the  finest  needle  through  the 
skin  at  any  place  you  are  sure  to  run  the 
needle  through  some  of  them  and  to  let  some 
blood  out. 

The  blood  keeps  flowing  on  through  them 
in  a  steady  stream. 

Veins. 

The  heart  sent  the  blood  out  through  the 
arteries  and  then  through  the  capillaries. 

Now  the  blood  goes  into  another  kind  of 
tube  called  a  vein.  The  veins  carry  the 
blood  back  to  the  heart  again. 


70  FIRST   BOOK    OF    PHYSIOLOGY 

Pull  up  your  sleeve  and  grasp  your  arm 
with  the  other  hand.  You  see  that  the  veins 
will  fill  up  with  blood.  This  blood  was  mov- 
ing up  the  arm,  but  your  hand  stopped  it. 
As  soon  as  you  let  go  it  will  move  on  back  to 


20. — Veins  in  the  arm. 

the  heart.  Many  of  the  veins  are  close  to 
the  surface  of  the  body,  and  you  can  see  that 
it  would  not  be  right  to  wear  any  tight  bands 
or  tight  clothing  on  any  part  of  the  body,  for 
that  would  stop  the  flow  of  blood  in  the  veins. 

Red  corpuscles. 

The  blood  looks  red,  but  it  is  not  all  red. 
I  drew  a  little  blood  from  my  thumb  and 
looked  at  it  with  a  microscope. 

In  picture  21  you  can  see  how  it  looked. 

The  little  round  bodies  are  called  red  cor- 
puscles. 

They  are  the  only  part  of  the  blood  that  is 
red.  There  are  so  many  of  them  that  they 
make  all  the  blood  look  red. 


THE   BLOOD  71 

The  red  corpuscles  are  so  small  that  you 
cannot  see  them  unless  you  look  through 
a  strong  microscope.  The  same  microscope 
that  made  the  blood  look  like  picture  2 1  made 
the  finest  kind  of  silk  look  like  picture  22. 

Old  people  do  not  have  as  many  red  cor- 
puscles in  their  blood  as  do  young  people, 
and  so  they  are  always  pale. 


2 1 .  — Red  blood-corpuscles. 

The  work  of  the  red  corpuscle  is  to  carry 
oxygen  from  the  lungs  out  to  all  parts  of  the 
body. 

White  corpuscles. 

There  are  also  many  white  corpuscles  float- 
ing along  in  the  blood  with  the  red  ones,  but 
not  nearly  so  many  of  them.  They  are  al- 
ways on  the  lookout  for  any  substance  that 


72  FIRST   BOOK   OF   PHYSIOLOGY 

may  harm  the  body.  They  try  to  keep  us 
from  getting  sick.  If  we  do  get  sick,  they  do 
their  best  to  make  us  well  again.  When  any 
of  the  little  germs  of  disease  get  into  the 
body,  they  try  to  kill  them  off.  If  the  white 
corpuscles  are  good  and  strong,  they  nearly 
always  succeed. 

When  you  cut  your  finger,  a  great  number 


22. — Fine  silk. 

of  them  will  hurry  to  that  spot  and  will  try 
to  heal  it.  The  white  matter  that  you  often 
see  in  a  sore  is  made  of  the  white  cor- 
puscles. 

They  are  our  body's  best  friends,  and  we 
ought  to  do  all  we  can  to  keep  them  strong 
and  in  good  health.  Alcohol  has  a  very  bad 
effect  on  them.  They  do  not  seem  to  care 


THE   BLOOD  73 

whether  they  work  or  not  when  alcohol  gets 
into  the  blood.  This  is  one  of  the  reasons 
a  hard  drinker  will  catch  a  disease  much 
quicker  than  other  persons.  The  nicotine  of 
tobacco  is  also  a  poison  to  them. 

A  man  who  drinks  whiskey  and  smokes 
cigarettes  is  more  likely  to  get  sick  than  a 
man  who  does  not  use  them,  and  then  it 
takes  a  longer  time  for  him  to  get  well. 

The  liquid  part  of  blood. 

The  corpuscles  are  carried  along  in  a 
liquid.  The  liquid  is  composed  of  water  and 
the  liquid  foods.  You  learned  a  little  while 
ago  that  the  meat  and  potatoes  and  other 
foods  were  changed  into  a  liquid  when  they 
were  digested  in  the  stomach  and  intestines. 
Now  we  find  this  food  in  the  blood,  and  the 
heart  keeps  pushing  it  out  through  the  ar- 
teries to  the  capillaries.  In  that  way  every 
part  of  the  body  gets  the  food  it  needs. 

Blood-clot. 

As  long  as  the  blood  is  moving  about  in 
the  body  it  is  a  very  thin  liquid,  but  it  will 
soon  form  into  a  clot  when  it  is  taken  out  of 
the  body.  When  you  cut  your  finger  or  any 
part  of  the  body  the  cut  will  soon  fill  up  with 


74  FIRST   BOOK   OF   PHYSIOLOGY 

a  thick  clot  of  blood.  If  it  is  not  a  very  bad 
cut,  the  clot  will  soon  stop  the  bleeding.  It  is 
good  for  us  that  this  is  so,  for  a  very  little  cut 
might  bleed  us  to  death  if  it  did  not  have  a 
way  of  stopping  itself.  When  a  large  artery 
is  cut  the  clot  cannot  stop  the  blood,  and  we 
have  to  hold  the  blood  in  till  a  doctor  comes 
and  ties  the  end  of  the  artery. 

Questions. 

1.  How  much  blood  is  in  your  body  ? 

2.  Describe  the  heart. 

3.  What  causes  tobacco  heart  ? 

4.  What  effect  does  beer  have  on  the  heart  ? 

5.  Describe  the  arteries. 

6.  What  can  you  do  when  an  artery  is  cut  ? 

7.  How  many  times  does  your  pulse  beat  in  one  minute  ? 

8.  Tell  about  the  capillaries. 

9.  What  is  the  use  of  the  veins  ? 

10.  What  makes  the  blood  red  ? 

1 1 .  What  work  do  the  red  corpuscles  have  to  do  ? 

12.  Of  what  use  are  the  white  corpuscles  ? 

13.  What  is  the  liquid  part  of  the  blood  ? 

14.  What  is  the  use  of  a  blood-clot  ? 


CHAPTER    VII 

BREATHING 

Why  we  breathe. 

THE  food  of  a  steam-engine  is  coal,  but  the 
coal  alone  will  not  make  a  fire.  There  must 
be  a  strong  draft  of  air.  When  we  have 
good  coal  and  a  good  draft,  then  we  can  have 
a  good  fire  and  can  get  up  steam,  and  the 
engine  will  do  work. 

A  man's  body  is  a  little  like  the  engine. 
Food  alone  will  not  keep  us  alive,  but  we 
must  breathe  in  the  air.  Then  the  food  and 
the  air  together  will  make  us  warm  and  en- 
able us  to  work. 

Something  for  you  to  do. 

Place  a  lamp-chimney  over  a  lighted  candle. 
Let  the  chimney  rest  on  two  pencils,  as  you 
see  in  picture  23.  The  candle-flame  will  be 
even  brighter  than  before.  A  little  smoke 
will  show  that  the  air  is  rushing  in  at  the  bot- 
tom of  the  chimney.  Now  take  the  pencils 
away  and  let  the  chimney  sit  down  on  the 
box  or  paper.  The  flame  will  soon  die  out 

75 


76  FIRST   BOOK   OF   PHYSIOLOGY 

because  it  cannot  get  fresh  air.  This  shows 
you  that  the  candle  alone  cannot  burn.  It 
takes  the  two  together  to  make  a  fire.  The 


23.  — Candle-flame. 


part  of  the  air  that  the  flame  wants  is  oxygen. 
Everything  that  is  alive,  even  the  trees  and 
the  grass,  must  have  oxygen  that  they  may 
live. 


BREATHING  77 

The  reason  we  breathe,  then,  is  that  we 
may  get  oxygen  to  combine  with  our  food. 
This  is  what  keeps  us  alive  and  makes  us 
able  to  think  and  work. 

The  nostrils. 

Air  should  be  breathed  in  through  the  nose 
and  not  through  the  mouth.  The  nostrils 
warm  the  air  before  it  gets  to  the  lungs,  and 
also  strain  out  the  dust  and  the  dirt.  Even 
when  you  run  or  work  hard  you  should 
breathe  through  the  nose.  Before  going  to 
sleep  be  careful  to  have  your  mouth  closed, 
and  lie  in  such  a  way  that  the  mouth  will  not 
drop  open  during  the  night. 

The  windpipe. 

A  large  tube  called  the  windpipe  conducts 
the  air  down  to  the  lungs.  Grasp  your  throat 
with  your  fingers  and  you  can  feel  that  this 
pipe  is  made  of  rings.  You  can  also  see  them 
in  picture  24.  They  are  not  hard  bone,  but 
are  so  stiff  that  the  windpipe  stands  open  all 
the  time.  On  the  top  of  the  windpipe  is  a 
lid  that  can  open  and  shut.  When  we  breathe 
it  is  open  ;  but  when  we  swallow  food  the  lid 
closes  down,  and  the  food  passes  over  it  and 
down  another  tube  called  the  gullet. 


78  FIRST    BOOK   OF    PHYSIOLOGY 

When  we  are  not  careful,  some  food  gets 
under  the  lid  and  into  the  windpipe,  and  we 
have  to  cough  hard  to  get  it  out. 

The  lungs. 

Each  of  us  has  a  pair  of  lungs.  If  you 
could  look  into  your  chest,  you  would  see 
your  lungs  and  heart  about  as  they  are  placed 
in  picture  25. 


24. — Air- tubes. 

The  lungs  are  not  firm  like  the  muscle  in 
your  arm,  but  are  soft  and  spongy.  When 
you  fill  your  lungs  with  air,  they  swell  up  and 
get  much  larger. 

Look  again  at  picture  24,  and  you  see  that 
the  windpipe  divides  at  its  lower  end  into 
two  branches.  One  branch  goes  to  each  lung. 
Then  these  divide  again  and  again  until  the 


BREATHING  79 

tubes  are  as  fine  as  a  hair  and  reach  every 
part  of  the  lung.  At  the  end  of  each  one  of 
the  fine  air-tubes  is  a  thin  little  air-sac.  When 
you  take  a  deep  breath,  it  is  like  blowing  up  a 
million  little  balloons  all  at  once. 


25. — The  lungs. 

Just  outside  the  little  air-sacs  are  fine  tubes 
that  carry  blood.  We  will  now  try  to  learn 
what  all  this  is  for. 

What  the  lungs  do. 

Awhile  ago  we  learned  that  when  the  blood 
went  out  through  the  body,  it  gave  up  its  food, 
and  the  red  corpuscles  gave  up  their  oxygen. 
The  blood  then  came  back  through  the  veins. 
Much  of  the  waste  matter  that  the  body  did 
not  want  any  more  came  back  with  it,  The 


8o  FIRST   BOOK    OF    PHYSIOLOGY 

corpuscles  are  not  red  any  more,  for  they  have 
lost  their  oxygen  and  are  now  purple  in  color. 
Such  blood  is  impure.  It  would  not  do  for 
the  heart  to  send  this  kind  of  blood  out  again. 
It  must  be  made  pure. 

The  right  heart  first  sends  it  into  the  lungs. 
There  the  blood  gets  ricl  of  the  waste  matter 
in  it,  and  the  corpuscles  load  up  with  oxygen 
and  turn  bright  red.  Now  it  comes  back  to 
the  heart,  and  the  left  heart  takes  it  and  sends 
it  out  over  the  body  again. 

Do  not  think  that  this  happens  to  all  the 
blood  at  one  time.  While  some  of  the  blood 
is  in  the  heart  and  lungs,  the  rest  of  it  is  out 
on  its  trip.  Some  is  in  the  head,  some  in  the 
arms  or  legs,  and  some  in  all  other  parts  of 
the  body.  After  awhile  this  blood,  too,  will 
come  back  to  the  heart  and  lungs. 

So  it  keeps  going  around  and  around.  It 
takes  about  twenty  seconds  for  a  drop  of 
blood  to  make  a  trip  from  the  left  heart  back 
to  the  left  heart  again. 

How  the  lungs  purify  the  blood. 

The  air  which  we  breathe  out  is  impure.  It 
was  changed  in  the  lungs. 

You  just  learned  that  each  air-sac  in  the 
lungs  is  surrounded  by  tiny  tubes  full  of  blood. 


BREATHING  81 

When  you  take  a  breath,  the  oxygen  of  the 
air  will  go  right  through  the  sides  of  the  air- 
sac  and  get  to  the  red  corpuscles  of  the  blood. 
The  gas  that  makes  the  blood  impure  is  called 
carbon  dioxide.  This  gas,  along  with  some 
other  waste,  comes  from  the  blood  over  into 
the  air-sac  and  then  we  breathe  it  out. 

Then  we  take  another  fresh  breath,  and  the 
same  thing  happens  again.  We  will  have  to 
keep  on  doing  this  as  long  as  we  live.  Breath- 
ing is  one  of  the  most  important  things  we 
have  to  do  ;  and  we  will  now  tell  you  some- 
thing about  pure  air  and  how  to  breathe. 

Cigarette  smoke. 

Any  boy  can  now  see  why  the  smoke  of  the 
cigarette  does  so  much  harm. 

The  cigarette  smoker  does  not  only  draw 
the  smoke  into  his  mouth  and  blow  it  out 
again.  That  would  be  bad  enough,  but  he 
inhales  it.  He  takes  it  down  into  all  the  little 
air-sacs,  where  it  gets  real  close  to  the  blood. 
The  lungs  are  trying  to  make  the  blood  pure, 
but  they  cannot  do  so  unless  we  give  them 
pure  air.  Cigarette  smoke  contains  a  deadly 
poison  called  nicotine.  This  poison  goes  from 
the  air-sacs  into  the  blood,  and  so  is  carried 
out  into  the  whole  body. 


82  FIRST   BOOK   OF    PHYSIOLOGY 

Is  it  any  wonder  that  cigarette  smoke  so 
quickly  ruins  the  health  of  the  body  and  of  thje 
mind  ? 

Pure  air. 

The  air  in  the  country  is  nearly  always  pure. 
That  is  the  reason  you  should  play  out  in  the 
park  or  take  a  romp  in  the  open  fields  or  work 
in  the  garden.  Exercise  will  do  you  no  good 
unless  you  can  get  good  air  at  the  same  time. 

In  the  crowded  city  the  air  often  gets  very 
bad,  even  in  streets.  The  worst  air  is  often 
found  in  the  rooms  where  we  live  and  where 
we  sleep.  We  cannot  always  tell  that  the  air 
is  bad  by  the  way  it  smells.  The  little  germs 
of  disease  are  so  small  that  we  cannot  see 
them,  and  yet  if  they  get  into  the  blood  they 
can  make  us  very  sick.  They  like  to  live  in 
damp,  dark  rooms,  but  the  sunlight  Avill  kill 
them.  Every  room  should  often  be  aired  out, 
and  the  sunlight  should  be  allowed  to  pour 
right  into  the  room  for  a  part  of  the  day. 

Sick  people  get  along  much  better  when 
they  can  lie  in  a  room  where  the  air  is  dry  and 
there  is  plenty  of  sunlight. 

We  cannot  help  breathing  some  of  these 
little  germs  into  our  lungs  every  day ;  but  if 
our  lungs  are  good  and  sound,  we  will  breathe 


BREATHING  83 

them  right  out  again,  and  they  can  do  us  no 
harm. 

How  the  breath  makes  air  impure. 

The  air  may  be  very  pure  when  we  take  it 
into  the  lungs,  but  it  is  not  pure  when  it 
comes  out.  We  take  some  of  the  oxygen 
out  of  the  air  every  time  we  fill  the  lungs,  and 
in  its  place  we  breathe  out  bad  air.  When 
you  stay  long  in  a  small  room  that  is  closed 
up  tight  you  get  sleepy  and  do  not  feel  well. 
This  is  because  the  air  is  getting  bad  and  you 
are  breathing  some  of  the  old  breath  over 
again.  If  you  let  in  fresh  air,  you  will  soon  get 
wide  awake  again  and  will  be  as  lively  as  ever. 

In  the  summer-time  most  people  can  have 
plenty  of  fresh  air,  for  then  the  windows  and 
doors  can  be  open. 

In  winter  the  coal-stove  or  grate  will  take 
out  a  great  deal  of  bad  air ;  but  if  there  are 
many  people  in  the  room,  the  window  should 
be  let  down  just  a  little  at  the  top  so  fresh  air 
can  be  coming  in  all  the  time. 

Something  for  you  to  do. 

Take  a  short  piece  of  a  candle  and  fasten 
it  to  a  wire,  as  you  see  in  the  picture.  Light 
the  candle  and  let  it  down  into  the  fruit-jar. 


84 


FIRST   BOOK    OF    PHYSIOLOGY 


It  still  burns  brightly.  Now  lift  the  candle 
out.  Put  your  mouth  close  down  onto  the 
mouth  of  the  jar  and  breathe  out  slowly  a 
long  breath  from  your  lungs.  Let  the  candle 
down  into  the  jar  again  and  it  will  burn  very 
dimly  or  go  clear  out.  Try  it. 


26. — Breath  and  candle  flame. 


The  candle  needs  oxygen  just  as  we  do. 
When  the  air  will  not  keep  a  candle  burning 
very  brightly,  it  is  certainly  not  fit  for  us  to 
breathe.  If  we  keep  on  breathing  bad  air  our 
life  will  grow  dim  or  will  go  out  just  like  that 
candle  light. 

If  a  mouse  be  put  into  a  jar  of  that  impure 
air  he  will  jump  about  for  a  short  time  and 


BREATHING  85 

then  fall  over  on  his  side.  He  is  not  dead, 
but  has  only  fainted.  If  you  shake  him  out 
onto  the  table  where  he  can  get  fresh  air  he 
will  soon  revive  and  run  off.  If  he  is  left 
in  the  jar  very  long,  he  will  die  because  he 
cannot  get  oxygen. 

Good  air  while  we  sleep. 

We  should  be  very  careful  to  have  good  air 
in  the  bedroom,  because  we  go  on  breathing 
all  night.  Before  you  go  to  sleep,  be  sure 
there  is  some  way  for  fresh  air  to  get  into  the 
room.  Open  a  window  a  little  from  the  top, 
no  matter  how  cold  it  is  on  the  outside.  Some 
people  sleep  in  summer-time  on  the  top  of 
their  houses,  so  they  can  be  sure  to  have 
plenty  of  fresh  air.  They  have  the  bed  inside 
a  cage  that  is  covered  only  with  a  thin  net  to 
keep  out  the  mosquitoes  and  other  insects. 
Some  sleep  in  tents  out  in  the  yard,  and  it 
always  gives  them  better  health.  This  shows 
how  important  it  is  for  all  of  us  to  breathe 
only  good  air. 

Because  some  boys  and  girls  are  afraid  in 
the  dark,  they  cover  themselves  up,  face  and 
all,  under  the  blankets.  Then  they  have  to 
breathe  the  bad  air  from  their  lungs  over  and 
over  again.  This  is  a  very  bad  thing  to  do. 


86  FIRST   BOOK   OF   PHYSIOLOGY 

Some  children  have  become  very  sickly  and 
have  suffered  from  bad  diseases  because  the/ 
slept  in  this  way. 

If  you  will  think  of  how  the  candle  acted 
in  bad  air,  you  will  not  go  to  sleep  again  with 
your  head  under  the  covers. 

How  often  we  should  breathe. 

I  have  just  counted  and  found  myself  taking 
fifteen  breaths  in  a  minute.  Then  I  stood  up 
and  took  some  rapid  exercise  and  then  counted 
again,  and  found  I  was  breathing  thirty  times 
in  a  minute.  You  try  it. 

When  we  do  hard  work  of  any  kind  the 
blood  must  go  around  faster.  The  heart 
beats  faster,  and  so  we  must  breathe  faster  to 
make  the  blood  pure. 

When  boys  run  a  long  race  they  breathe 
very  rapidly.  Some  cannot  run  very  far  till 
they  are  out  of  breath.  If  they  would  practise 
running  every  day,  and  would  learn  to  take  in 
deep  breath  only  through  the  nostrils,  they 
would  not  get  short  of  breath  for  a  long 
time. 

It  is  found  that  a  cigarette  smoker  soon 
gets  out  of  breath.  His  lungs  will  not  hold 
as  much  air  as  they  should.  The  tobacco 
has  spoiled  a  part  of  the  air-sacs,  hence  the 


BREATHING  87 

rest  of  them  have  to  be  filled  oftener  to  get 
the  right  amount  of  oxygen  to  the  blood. 

When  young  men  are  trained  for  athletic 
games,  like  foot-ball,  wrestling,  running,  and 
boxing,  they  are  not  allowed  to  use  any  to- 
bacco or  drink  any  beer  or  whiskey.  They 
tire  out  and  lose  their  breath  much  sooner 
when  they  smoke  or  drink,  and  are  almost 
sure  to  lose  the  game. 

Men  who  drink  alcohol  sometimes  get  so 
short  of  breath  that  they  cannot  lie  down. 
They  have  to  sit  up  all  the  time  for  fear  they 
may  smother  to  death. 

Taking  a  deep  breath. 

A  man's  lungs  will  hold  about  330  cubic 
inches  of  air.  That  is  a  little  more  than 
one  and  one-half  gallons.  When  he  fills  his 
lungs  full  he  can  then  breathe  out  230  cubic 
inches  of  air,  which  is  almost  exactly  one  gal- 
lon. Some  air  always  remains  in  the  lungs. 
Blowing  soap-bubbles  is  a  good  practice  in 
breathing.  If  you  can  blow  a  bubble  five  or 
six  inches  across,  with  one  breath,  you  are 
doing  very  well.  It  is  good  for  the  health  to 
take  fresh  air  deep  down  into  the  lungs  every 
once  in  a  while. 

We  should  learn  to  sit  and  walk  with  the 


88  FIRST   BOOK   OF   PHYSIOLOGY 

chest  forward  and  the  shoulders  back.  This 
gives  the  lungs  room,  and  then  it  is  easy  tc 
fill  them  with  air. 

Some  girls  have  a  very  bad  fashion  of 
fastening  the  dress  very  tight  about  the 
waist.  This  cramps  the  lungs.  Such  a  girl 
cannot  take  a  full  breath.  She  tries  to  make 
up  for  it  by  breathing  faster,  but  she  will 


27. — A  soap-bubble. 

be  sure  to  have  poor  blood  and  poor  health. 
The  lungs  must  get  enough  air  so  that  each 
red  corpuscle  can  get  its  load  of  oxygen,  and 
also  the  poison  in  the  bad  blood  must  get  out 
into  the  air.  This  can  never  be  done  well 
when  the  lungs  are  squeezed  out  of  shape. 

It  is  very  good  for  any  one  to  go  to  an 
open  window  or  out  onto  the  porch  and  take 
five  or  six  deep  breaths  every  day,  winter  and 


BREATHING  89 

summer.  Fill  the  lungs  full  and  hold  it  there 
for  a  while.  Then  breathe  out  and  fill  them 
again. 

If  you  will  practise  this  and  make  sure  that 
you  always  get  plenty  of  good  air  to  the  lungs, 
it  is  quite  likely  you  will  never  catch  a  cold. 

How  the  body  is  kept  warm. 

When  coal  is  burning  in  a  stove,  you  know 
that,  if  it  can  get  a  good  draft  of  air,  it  will 
make  the  stove  very  hot.  If  you  want  the  coal 
to  quit  burning,  you  close  the  damper  so  the 
air  cannot  get  in. 

The  oxygen  of  the  air  which  you  breathe  is 
carried  by  the  red  corpuscles  out  even  to  the 
tips  of  the  fingers  and  toes.  When  it  unites 
with  the  food,  it  makes  heat  just  as  it  did  with 
the  coal  in  the  stove.  There  is  no  blaze  of 
fire  in  the  body  like  the  one  in  the  stove,  but 
the  food  is  slowly  burned,  and  that  keeps  our 
bodies  warm. 

Just  warm  enough. 

Our  bodies  must  not  get  too  warm  nor  too 
cold.  Look  at  the  thermometer  in  your  house 
or  school-room.  It  ought  to  show  a  tempera- 
ture of  70  degrees.  Your  body  on  the  inside 


90  FIRST   BOOK   OF   PHYSIOLOGY 

is  28  degrees  warmer  than  that.  That  would 
make  your  temperature  98  degrees. 

It  will  be  almost  exactly  98  as  long  as  you 
are  not  sick.  If  you  get  a  fever,  your  tem- 
perature may  go  up  to  103  or  104  degrees. 
Then  the  doctor  says  you  are  very  sick. 

No  part  of  our  body  can  do  its  best  work 
unless  its  temperature  is  98  degrees  or  very 
close  to  it. 

In  winter-time  we  wear  heavy  clothes  to 
keep  the  heat  in  our  bodies  from  getting  away, 
and  we  live  in  warm  rooms  for  the  same 
reason. 

Another  good  way  to  keep  warm  is  by  exer- 
cise. When  we  make  our  muscles  work,  the 
food  is  burned  up  faster,  and  that  makes  us 
warmer.  Good  exercise  in  the  cool  fresh  air 
is  a  much  better  way  to  get  warm  than  to  sit 
all  day  by  a  warm  stove. 

We  can  nearly  always  manage  to  keep  our 
bodies  from  getting  too  cold,  but  there  is  often 
danger  that  they  may  get  too  hot.  The  body 
has  a  very  nice  way  of  keeping  itself  from 
getting  too  warm,  and  we  will  study  that  next. 

How  sweat  cools  us. 

When  the  body  gets  too  warm,  the  sweat 
begins  to  pour  out  all  over  the  surface  of  the 


BREATHING  91 

skin.  As  soon  as  the  sweat  gets  to  the  air,  it 
begins  to  dry  up,  and  that  takes  heat  from  the 
body.  This  is  a  way  nature  has  to  keep  us 
from  getting  too  hot. 

Put  a  drop  of  gasoline  on  the  back  of  your 
hand,  and  it  will  feel  very  cool  because  it 
dries  up  so  quickly. 


28. — A  water- jug. 

Dip  one  of  your  hands  into  warm  water, 
and  then  hold  both  hands  up  where  the  wind 
is  blowing.  The  wet  hand  will  feel  much 
cooler  than  the  dry  one,  even  if  the  water  is 
very  warm. 

In  some  warm  countries  they  make  their 
water-jugs  out  of  clay  that  is  much  like  our 
flower-pots.  The  water  will  soak  through  the 


92  FIRST   BOOK   OF   PHYSIOLOGY 

sides  of  the  jug  and  keep  it  wet  on  the  out- 
side. Then  they  hang  the  jug  up  where  the 
wind  is  blowing,  and  after  a  while  the  water  is 
nice  and  cool.  Sweat  cools  our  bodies  in  just 
the  same  way. 

The  picture  shows  you  a  water-jug  of  this 
kind.  This  one  was  used  by  a  boy  in  Cuba. 

Will  alcohol  warm  the  body. 

Some  men  think  that  if  they  take  a  drink 
of  whiskey  or  beer  on  a  cold  day  it  will  keep 
them  warm. 

It  has  been  found  out  that  this  is  a  mistaken 
notion.  Alcohol  will  soon  make  the  body 
colder.  When  a  man  drinks  whiskey,  a  great 
deal  of  the  warm  blood  will  come  to  the  sur- 
face of  the  body  just  under  the  skin.  The 
heat  can  then  easily  get  away.  He  will  lose 
more  heat  than  the  alcohol  can  give  him. 
Then,  too,  his  food  will  not  burn  as  well  as  it 
did  before.  The  alcohol  smothers  out  his  fire. 
A  man  who  uses  strong  drinks  will  freeze  to 
death  sooner  than  those  who  do  not. 

The  very  best  way  to  keep  warm  is  to  eat 
a  hearty  meal,  take  full  breaths  of  fresh 
air,  and  keep  the  blood  in  rapid  motion  by 
exercise. 


BREATHING  93 

A  story. 

One  very  cold  day  six  men  started  out  on 
a  long  trip.  They  had  food  enough  with 
them  to  last  for  three  days.  After  they  had 
travelled  for  two  days  it  grew  bitter  cold,  and 
they  lost  their  way.  Soon  it  began  to  get 
dark.  They  could  make  no  fire,  for  they 
could  find  no  wood  to  burn.  They  thought 
they  would  all  surely  freeze  to  death  before 
morning.  Their  leader  told  them  all  to  eat 
heartily  of  the  food  they  had  with  them,  for 
he  knew  that  was  the  only  way  they  had  to 
keep  warm. 

Then  they  ran  about  and  took  all  sorts  of 
exercise  to  get  warm,  but  they  were  not  able 
to  do  this  all  night. 

So  they  spread  a  blanket  on  the  ground, 
and  all  lay  down  very  close  together  and  cov- 
ered themselves  as  best  they  could.  Just 
before  this  three  of  the  men  took  a  large 
drink  of  strong  whiskey.  They  thought  it 
would  help  to  keep  them  warm.  The  other 
three  believed  they  could  get  along  better 
without  it.  They  were  all  so  tired  that  they 
went  to  sleep.  The  next  day  they  were 
found  there,  but  the  three  men  who  drank 
the  whiskey  were  frozen  to  death.  The  other 
three  had  suffered  very  much  with  the  cold, 


94  FIRST   BOOK    OF    PHYSIOLOGY 

but  not  even  their  little  toes  were  frozen. 
Their  food  and  breath  kept  making  heat  all 
night  and  kept  them  from  freezing. 

Questions. 

1 .  What  two  things  make  fire  burn  ? 

2.  Tell  about  the  experiments  with  the  candle  and  lamp- 
chimney.      Have  you  tried  it  ? 

3.  Why  should  we  breathe  through  the  nose  ? 

4.  Describe  the  windpipe. 

5.  Tell  about  the  air-tubes  and  air-sacs  in  the  lungs. 

6.  Why  is  the  blood  sent  through  the  lungs  ? 

7.  How  is  the  blood  purified  in  the  lungs  ? 

8.  Why  is  cigarette  smoke  so  harmful  ? 

9.  Tell  all  you  can  about  pure  and  impure  air. 

10.  What  makes  the  air  in  a  room  impure  ? 

1 1.  Show  the  effects  of  breath  on  a  candle  flame. 

12.  How  can  we  have  fresh  air  while  we  sleep  ? 

13.  How  often  do  you  breathe  ? 

14.  How  much  air  will  the  lungs  hold  ? 

15.  What  keeps  the  body  warm  ?    How  warm  should  it  be  ? 

1 6.  How  do  clothes  keep  us  warm  ? 

17.  How  does  sweat  cool  the  body  ? 

1 8.  Tell  the  story  of  the  six  men. 


CHAPTER    VIII 

THE   SKIN 

What  the  skin  is. 

THE  skin  is  a  thin  covering  stretched  all 
over  the  outside  of  the  body.  There  are  two 
layers  of  skin.  The  outside  one  is  called  the 
scarf-skin,  and  right  under  it  is  a  second  layer 
called  the  true  skin.  The  scarf-skin  is  thin, 
but  it  may  grow  quite  thick.  A  man  who 
works  every  day  with  a  shovel  or  pick  will 
have  a  hard,  thick  scarf-skin  on  the  palms  of 
his  hands.  Corns  on  the  feet  are  caused  in 
the  same  way  by  the  rubbing  of  the  shoes. 
You  see  how  the  body  tries  to  protect  itself 
by  making  the  skin  hard  and  tough  wherever 
it  is  needed.  A  little  cut  or  scratch  in  the 
skin  will  soon  show  us  how  useful  the  skin  is 
as  a  protection  to  the  tender  parts  under  it. 

This  outside  skin  is  a  great  deal  like  the 
outside  bark  of  a  tree.  The  bark  may  be 
called  the  skin  of  the  tree.  In  the  centre  of 
the  tree  is  the  hard  wood.  Around  it  is  a 
tender  bark,  which  is  a  little  like  our  true 
skin.  Outside  of  all  is  the  rough  bark,  which 

95 


96  FIRST   BOOK   OF   PHYSIOLOGY 

is  like  our  scarf-skin.  You  can  cut  away  the 
bark  without  hurting  the  tree  if  you  do  no; 
cut  too  deep. 


Nails. 

The  scarf-skin  is  not  the  same  all  over  the 
body.  On  the  tops  of  the  fingers  and  toes 
it  changes  to  a  harder  substance,  called 
finger-nails  and  toe-nails.  The  nails  keep 
growing  out  all  the  time,  and  we  have  to  pare 
them  off.  They  need  care,  and  should  be 
cleaned  every  day.  Some  boys  and  girls 
have  a  bad  habit  of  biting  their  finger-nails,  so 
they  always  look  rough  and  ragged.  Such  a 
hand  never  looks  well. 

Hair. 

On  the  head  is  a  heavy  growth  of  hair. 
This  also  is  a  part  of  the  scarf-skin.  The 
hair  is  alive  but  it  cannot  feel,  and  so  it  does 
not  hurt  to  cut  it.  In  picture  30  you  can  see 
the  root  of  a  hair.  It  is  deep  down  in  the 
skin.  A  tiny  blood-tube  runs  into  the  bottom 
of  each  hair  and  brings  it  its  food.  On  each 
side  of  it  you  see  a  little  sac,  which  holds  a 
kind  of  oil.  This  is  poured  onto  the  hair  and 
keeps  it  soft  and  glossy. 


THE   SKIN  97 

Care  of  the  hair. 

A  fine  head  of  hair  makes  one  look  a  great 
deal  better.  It  also  protects  the  head  and 
keeps  one  from  catching  cold  easily.  We 
must  take  proper  care  of  the  hair  if  we  want 
it  to  be  in  good  condition.  The  scalp  and 
hair  will  get  dirty,  and  must  be  washed  once 
in  a  while,  but  not  too  often.  It  is  not  good 
to  wet  the  hair  every  time  you  wash  your 
face,  for  that  will  make  it  lose  its  gloss  and 
become  brittle.  Comb  the  hair  dry,  and  every 
few  days  brush  the  scalp  briskly  with  a  hair- 
brush. It  does  no  good  to  put  oil  on  the  hair. 
If  the  scalp  is  healthy,  it  will  give  the  hair  all 
the  oil  that  it  needs. 

How  the  scarf-skin  protects  us. 

If  you  have  ever  tried  to  pick  a  splinter 
from  your  hand  or  foot,  you  know  that  the 
skin  is  very  tough. 

The  butcher  always  saves  the  skin  of  a 
calf  or  ox  because  it  can  be  used  in  making 
boots  and  shoes.  It  is  hard  to  get  through 
the  skin  to  the  tender  parts  under  it.  The 
little  germs  of  disease  would  like  to  get  in 
where  the  blood  and  tender  flesh  are,  but  the 
skin  acts  like  the  walls  of  a  castle  and  keeps 

7 


98  FIRST   BOOK   OF   PHYSIOLOGY 

these  enemies  out.  You  can  even  take 
poison  into  your  hand,  and  it  cannot  easily 
get  to  the  blood  unless  the  skin  is  cut  or 
scratched. 

It    hurts    when    you    are   stung  by   a    bee, 
because    he    makes    sure    to    put    his   poison 


29. — A  bee-sting. 

under  the  scarf-skin.  You  can  see  in  this 
picture  a  bee-sting  as  it  looks  under  a  mi- 
croscope. The  point  is  finer  than  the  sharp- 
est needle,  so  that  he  may  be  sure  to  push 
it  through  the  tough  skin  when  he  stings 
us. 


THE    SKIN  99 

The  color  of  the  skin. 

Between  the  scarf-skin  and  the  true  skin 
are  little  grains  of  coloring  matter. 

These  are  the  cause  of  the  difference  in  the 
color  of  the  skin  of  different  people. 

The  grains  are  very  numerous  and  black  in 
the  Negro.  In  some  people  they  are  yellow. 
In  white  people  they  are  of  a  light  color,  but 
when  the  sun  shines  upon  the  skin,  they  get 
darker,  and  then  we  say  the  skin  is  tanned. 
In  many  people  these  grains  are  collected  in 
spots,  and  when  the  sun  makes  these  spots 
darker,  we  call  them  freckles. 

A  few  people  have  no  coloring  matter  in 
the  skin  at  all.  This  is  unfortunate.  They 
look  very  pale  ;  and  even  their  eyes  and  hair 
are  not  colored  as  they  are  in  other  people. 
Such  persons  are  called  Albinoes. 

A  study  of  the  picture. 

The  picture  30  shows  you  about  how  the 
skin  would  appear  if  you  could  look  down 
into  it  and  see  everything  very  much  en- 
larged. 

At  the  top  is  the  layer  of  scarf-skin,  which 
is  also  called  the  epidermis.  Below  it  is  the 
thicker  layer  called  the  true  skin. 


100 


FIRST    BOOK    OF    PHYSIOLOGY 


At  the  top  of  the  true  skin  you  see  ridges 
and  points.  These  are  called  papillae.  The;ye 
are  the  ends  of  the  nerves  of  feeling. 

Running  down  through  both  layers  of  the 
skin  are  tubes,  which  you  can  see  are  coiled 


30.— The  skin. 


up  at  the  lower  ends.  These  are  the  sweat- 
tubes.  The  picture  also  shows  one  hair  and 
its  oil  sacs.  These  sacs  are  called  sebaceous 
glands.  -The  fat  in  the  skin  makes  it  smooth 
and  plump. 


THE    SKIN 

Nerves  of  feeling. 

The  nerves  of  feeling  are  just  below  the 
scarf-skin  all  over  the  body.  When  the  least 
thing  touches  the  body,  these  nerves  report  it 
to  the  mind.  If  it  were  not  for  this,  we  might 
often  be  severely  hurt  without  knowing  it. 

These  nerves  of  feeling  are  very  numerous 
on  the  ends  of  the  fingers,  but  there  are  only 
a  few  on  our  backs.  Can  you  tell  why  this  is 
so? 

Sweat-pores. 

The  surface  of  the  skin  is  full  of  little  open- 
ings called  pores.  They  are  the  ends  of  the 
sweat-tubes.  There  are  a  great  number  of 
them.  Nearly  20,000  of  them  are  on  the  palm 
of  the  hand  alone. 

The  sweat-tubes  bring  water  and  waste 
matter  from  the  blood  out  through  the  pores. 
When  the  pores  are  stopped  up  in  any  way, 
the  poison  and  water  cannot  get  out.  If  all 
or  most  of  your  pores  are  stopped,  you  will 
get  very  sick. 

Bathing. 

You  can  now  see  plainly  why  we  ought  to 
keep  the  body  clean.  There  are  several  good 
reasons  for  bathing.  The  sweat  often  pours 


io2,          FIRST   BOOK   OF   PHYSIOLOGY 

out  on  the  skin,  where  it  gets  mixed  with  dust 
and  dirt  that  dries  and  closes  the  pores. 

The  skin  is  also  kept  oily  so  it  will  not 
break  or  crack.  This  oil  also  gathers  dirt. 

Then  the  scarf-skin  is  growing  out  all  the 
time,  and  its  loose  scales  need  to  be  rubbed 
off.  Bathing  keeps  the  pores  of  the  skin 
open  so  the  sweat-tubes  can  do  their  work. 
At  least  once  every  week  the  body  should  be 
washed  all  over.  In  summer  we  need  a  bath 
oftener  than  in  winter. 

If  you  have  a  bath-tub  in  your  home,  so 
much  the  better  ;  but  you  can  keep  the  skin 
clean  without  it. 

A  large  basin  of  soft  water,  a  sponge  or 
wash-rag,  some  good  mild  soap,  and  one  or 
two  large  towels,  are  all  that  is  needed  for  a 
good  bath.  After  bathing  you  must  be  sure 
to  rub  with  the  towels  until  the  skin  is  pink 
and  real  dry. 

If  you  will  be  careful  about  the  rubbing, 
there  will  be  little  danger  of  catching  a  cold 
after  a  bath. 

Clean  clothing. 

The  clothing  next  to  the  skin  will  soon  get 
dirty.  Even  when  it  looks  white,  it  may  hold 
a  great  deal  of  waste  matter  that  has  come 


THE   SKIN  103 

out  of  the  pores  of  the  skin.  Such  clothing 
must  be  often  washed,  not  only  for  the  sake 
of  our  own  health,  but  to  make  ourselves 
agreeable  to  other  people. 

When  you  go  to  bed,  all  the  clothes  you 
wore  in  the  daytime  should  be  taken  off,  and 
only  a  night-dress  should  be  worn  while  you 
sleep. 

A  good  bath,  a  clean  night-dress,  and  clean 
bedclothes  will  help  you  to  sleep  soundly. 


How  to  have  a  clear  skin. 

People  who  have  good  health  always  have  a 
nice  clear  skin.  The  best  way  to  have  a  good 
complexion  is  to  take  good  care  of  the  health 
of  the  whole  body.  When  we  eat  too  much 
or  do  not  eat  the  kind  of  food  that  is  good  for 
us,  the  skin  will  often  get  coarse  and  will  break 
out  in  pimples. 

Simple,  coarse  food  will  make  the  best  com- 
plexion. You  remember  the  story  of  the  four 
boys  who  would  not  eat  the  king's  meat,  but 
wanted  only  their  simple  kind  of  food.  When 
they  came  before  the  king,  he  said  they  were 
fair  to  look  upon. 

If  the  skin  is  not  healthy,  it  will  do  no  good 
to  put  any  kind  of  wash  or  powder  upon  it. 


io4          FIRST   BOOK   OF   PHYSIOLOGY 

Nothing  but  good  health  will  make   a  good 
complexion. 


Effect  of  alcohol  on  the  skin. 

The  true  skin  is  full  of  fine  blood-tubes. 
Alcohol  makes  these  tubes  larger,  and  then 
too  much  blood  is  found  in  the  skin.  After  a 
while,  if  a  man  keeps  on  drinking,  these  tubes 
will  stay  larger  all  the  time.  This  makes  the 
face  red.  You  can  tell  an  old  drinker  by  the 
appearance  of  his  nose.  It  is  swollen  and 
very  red.  His  eyes  are  blood-shot  for  the 
same  reason. 

The  man  who  drinks  whiskey  or  beer  or  any 
strong  drink  soon  gets  so  he  does  not  care 
about  his  health.  He  allows  his  skin  to  get 
very  dirty,  and  then  it  will  not  do  its  share  of 
throwing  off  the  waste  and  poisons  of  the 
body.  Alcohol  puts  so  much  poison  into  the 
body  that  even  a  healthy  person  could  not  get 
rid  of  it  all. 

When  the  body  is  not  in  good  health,  it  is 
much  easier  to  catch  any  disease  that  comes 
along.  The  drunkard  is  the  first  to  catch 
diseases  and  is  much  more  apt  to  die  when  he 
gets  them.  He  is  not  strong  enough  to  fight 
them  off.  This  is  the  reason  a  doctor  does 


THE   SKIN  105 

not  have  much  hope  for  a   drinker  when  he 
gets  real  sick. 

The  surgeon  does  not  like  to  cut  through 
the  skin  and  operate  on  an  old  drinker  be- 
cause he  knows  his  patient  is  apt  to  die  in  the 
operation,  and  if  he  does  live,  it  will  take  a 
long  time  for  the  cut  to  heal. 

Effect  of  tobacco  on  the  skin. 

The  evil  effects  of  tobacco  can  be  seen  in 
the  skin  as  well  as  in  the  rest  of  the  body, 
When  a  man  takes  a  strong  poison  like  nico- 
tine, every  part  of  his  body  must  suffer.  It 
does  most  harm  to  boys  under  twenty-one 
years  of  age. 

The  skin  tries  to  throw  off  the  tobacco 
poison,  but  it  has  enough  to  do  without  that. 
When  you  give  it  too  much  extra  work  it  can 
do  nothing  well. 

When  a  tobacco  user  comes  out  of  the 
bath  you  can  often  smell  the  tobacco  in  the 
water. 

The  skin  of  a  boy  who  smokes  cigarettes 
becomes  sallow  and  has  an  unhealthy  look. 
This  cannot  be  cured  by  bathing  and  rubbing 
the  skin.  The  only  way  is  to  let  tobacco  alone, 
and  then  the  body  will  cure  itself. 


io6          FIRST   BOOK    OF    PHYSIOLOGY 

Questions. 

1 .  Tell  about  the  two  layers  of  skin. 

2.  Tell  all  you  can  about  the  nails. 

3.  Describe  a  hair. 

4.  How  can  the  hair  be  cared  for  ? 

5.  Why  is  the  scarf-skin  made  so  tough  ? 

6.  What  gives  the  skin  its  color  ? 

7.  Tell  about  the  parts  you  can  see  in  picture  30. 

8.  What  is  the  use  of  the  nerves  of  feeling  in  the  skin  ? 

9.  What  is  the  use  of  the  sweat-pores  ? 

10.  Why  should  we  bathe  ? 

1 1 .  What  is  the  best  way  to  have  a  good  complexion  ? 

1 2.  What  bad  effects  does  alcohol  have  on  the  skin  ? 

13.  What  bad  effects  does  tobacco  have  on  the  skin  ? 


CHAPTER   IX 

EXCRETION 

How  the   body  gets  rid  of  poisons  and  waste. 

THIS  is  a  short  chapter,  but  a  very  important 
one.  Our  good  health  and  our  very  life  de- 
pend on  how  well  we  can  get  rid  of  poisons 
and  waste.  Poisons  are  often  taken  into  the 
body  with  the  food  and  drink.  Poisons  are 
made  inside  of  the  body  itself,  and  there  is 
always  a  great  deal  of  waste  matter  that  must 
be  thrown  out. 

The  most  of  this  kind  of  work  is  done  by 
the  lungs,  the  liver,  the  skin,  the  kidneys,  and 
the  intestines. 

The  lungs. 

We  have  learned  that  the  air  that  comes 
from  the  lungs  is  impure  because  it  is  loaded 
with  a  waste  called  carbon  dioxide.  It  got  this 
from  the  blood  in  the  lungs.  Besides  this  a 
great  deal  of  water  comes  out  with  the  breath. 
The  carbon  dioxide  is  a  gas,  and  so  we  cannot 

see  it,  but  you  can  show  that  it  is  there  by 

107 


io8          FIRST   BOOK   OF   PHYSIOLOGY 

trying  the  experiment  we  told  you  about  on 
page  76  of  this  book. 

You  can  easily  find  the  water  in  your  breath 
by  breathing  against  a  cold  window-pane. 
The  water  will  collect  on  the  glass.  On  a 
cold  day  you  say  you  can  see  your  breath. 
This  is  only  water  taken  from  the  blood,  and 
when  it  strikes  the  cold  air  it  forms  into  very 
small  drops  like  fog. 

The  breath  works  for  us  both  when  it  goes 
in  and  when  it  comes  out.  When  it  goes  in  it 
carries  oxygen  to  the  blood  and  when  it  comes 
out  it  brings  waste  and  poisons  from  the  blood. 

The  liver. 

The  liver  is  a  very  important  part  of  the 
body.  We  told  you  something  about  it  on 
pages  55  and  57.  Read  that  again. 

If  your  liver  would  cease  to  work  for  only 
a  short  time  you  would  get  sick  and  die. 

It  gathers  up  many  poisonous  substances 
from  the  liquid  food  and  the  blood.  It  takes 
out  the  bile  and  turns  it  to  good  use  in  diges- 
tion. A  healthy  liver  will  always  do  its  work 
well  if  we  do  not  give  it  too  much  to  do. 

o 

If  we  eat  too  much,  or  eat  food  that  is  not 
good  for  us,  we  may  give  the  liver  more  work 
than  it  is  able  to  do.  Then  some  bad  blood 


EXCRETION  109 

gets  past  it  and  we  get  sick.  When  a  man 
drinks  alcohol  he  always  overloads  his  liver. 
Alcohol  is  a  poison,  and  the  liver  tries  to  keep 
it  out  of  the  blood.  While  it  is  doing  this,  it 
cannot  do  its  other  work  in  the  right  way. 

Alcohol  also  spoils  the  digestion  of  the  food, 
and  that  throws  more  work  onto  the  liver.  An 
old  drinker's  liver  gets  weaker  and  smaller, 
and  so  you  can  see  that  alcohol  gives  the  liver 
more  to  do  and  then  makes  it  weaker  so  that 
it  cannot  do  it. 

The  kidneys. 

There  are  two  kidneys  in  the  human  body, 
one  on  each  side  of  the  backbone  at  the  small 
of  the  back.  Each  kidney  has  the  shape  of 
a  bean,  and  is  about  four  inches  long,  two  and 
one-half  inches  broad,  and  one  inch  thick. 

Their  work  is  to  take  water  and  several 
kinds  of  poisons  and  minerals  out  of  the  blood. 
When  they  do  not  work  right,  we  soon  know 
that  something  is  going  wrong  with  us. 

The  water  washes  away  the  poisons  that  the 
kidneys  gather  up.  We  should  drink  plenty 
of  water.  The  skin  and  lungs  are  throwing 
off  water  all  the  time,  and  the  kidneys  take 
out  about  three  pints  every  day,  and  the  body 
needs  a  great  deal  all  the  time. 


no  FIRST    BOOK   OF    PHYSIOLOGY 

It  will  do  no  harm  to  drink  good  water  even 
when  you  are  not  thirsty.  If  you  get  toe 
much  the  kidneys  and  skin  will  soon  take  it 
away,  and  it  will  carry  poisons  and  waste  out 
with  it. 

A  man  can  live  a  long  time  without  other 
foods,  but  he  would  hardly  get  through  a  single 
day  without  water. 

We  have  already  told  you  about  the  work 
done  by  the  skin  and  the  intestines,  and  so 
we  end  this  chapter  here. 

Questions. 

1.  How  do  poisons  get  into  the  body  ? 

2.  How  are  the  wastes  and  poisons  taken  out  of  the  body  ? 

3.  Tell  what  the  lungs  do. 

4.  Tell  what  the  liver  does. 

5.  Describe  the  kidneys. 

6.  What  work  is  done  by  the  kidneys  ? 

7.  Why  should  we  drink  plenty  of  good  water  ? 

8.  What  two  things  does  breathing  do  for  us  ? 


CHAPTER    X 

THE   BRAIN,   SPINAL  CORD,   AND    NERVES 

How  the  body  is  governed. 

THE  brain  is  the  ruler  of  the  body.  The 
muscles  may  be  strong,  but  they  will  not  move 
till  the  brain  sends  out  an  order  to  them. 
Everything  the  body  does  is  governed  by  the 
brain.  The  muscles  are  like  an  army  of  sol- 
diers, and  the  brain  is  like  their  general.  All 
the  messages  of  the  soldiers  are  sent  in  to  the 
general,  and  then  his  orders  are  sent  out  to 
the  soldiers.  If  the  army  is  well  trained,  it 
will  do  only  what  it  is  ordered  to  do,  and  will 
not  move  until  it  gets  orders  from  the  general. 
In  the  same  way,  if  our  muscles  are  well 
trained,  they  will  carry  out  the  orders  of  the 
brain. 

What  the  brain  is. 

The  brain  is  made  of  a  soft,  delicate  sub- 
stance. It  is  very  easily  harmed,  and  so  it  is 
enclosed  in  a  hard,  bony  case  called  the  skull. 
The  brain  weighs  about  three  pounds.  It  is 

gray  on  the  outside  and  white  on  the  inside. 

in 


ii2          FIRST   BOOK   OF   PHYSIOLOGY 

If  you   could   see   the   top  of   your  brain,   it 
would  look  like  what  you  see  in  picture  31; 


31. — The  brain. 

It  is  not   smooth  on  the  surface,  but  lies  in 
folds  or  ridges. 

The  spinal  cord. 

The  spinal  cord  of  a  man  is  about  eighteen 
inches  long  and  about  as  thick  as  the  little 
finger.  At  its  upper  end  it  is  connected  with 
the  brain  and  runs  down  through  the  back- 
bone. 

You  have  learned  that  the  backbone  is 
made  up  of  a  number  of  bones  placed  one  on 
top  of  the  other.  Each  one  has  a  hole  through 


BRAIN,  SPINAL   CORD,  AND  NERVES     113 

it,  as  you  can  see  in  picture  32.  Altogether 
these  holes  make  a  long  tube  and  in  it  the 
spinal  cord  is  placed.  This  makes  a  strong 
covering  for  it.  It  is  very  tender,  like  the 
brain,  and  so  it  can  be  easily  hurt. 


32. — A  vertebra. 

You  can  easily  see  how  the  spinal  cord  is 
placed  inside  the  bones  if  you  will  examine  the 
neck  of  a  chicken.  The  next  time  you  have 
chicken  for  dinner  pull  apart  the  bones  of  the 
neck  and  you  will  find  the  spinal  cord  inside. 

Nerves. 

The  nerves  are  fine  white  threads  that  run 
out  from  the  brain  and  spinal  cord  to  every 
part  of  the  body.  The  brain  could  not  send 


ii4  FIRST   BOOK    OF    PHYSIOLOGY 

an  order  to  the  hand  or  foot  unless  it  had  a 
nerve  to  send  the  message  on. 

There  are  many  telephones  in  a  town,  and  a 
wire  runs  from  each  one  to  a  central  telephone 
office.  Messages  are  going  back  and  forth 
over  some  of  the  wires  all  the  time,  so  that 
the  central  office  is  kept  very  busy.  Your 
telephone  would  be  of  no  use  to  you  without 
the  wires.  In  the  same  way  the  brain  cannot 
control  the  body  without  the  nerves.  One 
pair  of  nerves  comes  from  the  brain  out  to  the 
eye  and  we  use  it  to  see.  If  these  nerves 
were  cut  in  two  we  would  be  entirely  blind,  no 
matter  how  good  the  eyes  might  be.  Another 
pair  goes  to  the  ear  and  we  use  them  to  hear. 
Another  pair  runs  to  the  nose  and  still  another 
to  the  mouth,  and  we  use  them  to  smell  and 
taste. 

A  great  number  of  nerves  run  from  the 
brain  down  through  the  backbone.  These 
are  tied  up  into  a  bundle  which  we  have  called 
the  spinal  cord. 

At  a  number  of  places  along  the  backbone 
we  find  holes  in  the  sides  of  the  bones.  Nerves 
branch  off  from  the  spinal  cord  and  come  out 
through  these  holes  to  all  parts  of  the  body. 

A  large  nerve  is  only  a  bundle  of  a  great 
many  smaller  ones.  It  is  like  one  of  the  large 


BRAIN,  SPINAL   CORD,  AND    NERVES    115 

cables  which  you  see  on  the  telephone  poles 
near  the  central  office.  Two  or  three  hundred 
wires  are  often  put  inside  a  lead  tube  and  each 
wire  covered  so  it  cannot  touch  the  others. 
A  large  nerve  is  made  up  a  great  deal  like 
that.  It  keeps  branching  off  and  getting 
smaller  and  smaller  till  it  is  so  fine  you  cannot 
see  it  without  a  strong  microscope. 

What  the  brain  does. 

The  brain,  the  spinal  cord,  and  the  nerves  are 
together  called  a  nervous  system.  We  have 
just  learned  something  about  what  the  parts 
of  this  system  are  and  where  they  are.  Let 
us  now  try  to  find  out  what  they  do. 

The  brain  is  the  most  important  part  of  our 
bodies.  We  use  the  brain  when  we  think.  If 
the  brain  is  good  and  healthy,  we  can  get  good 
lessons  and  can  think  well.  We  use  the  brain 
to  work  out  examples  in  arithmetic  or  to  pre- 
pare lessons  in  geography  and  language  and 
spelling.  When  a  boy  or  girl  does  not  have 
good  lessons,  we  think  that  he  either  does  not 
have  a  good  brain  or  he  is  not  making  good 
use  of  it. 

We  make  our  brains  stronger  by  using 
them.  The  more  we  think  the  better  we  can 
think.  One  thing  you  learned  about  the  mus- 


n6          FIRST   BOOK   OF   PHYSIOLOGY 

cles  was  that  they  would  grow  strong  by  use. 
It  is  the  same  with  the  brain.  A  lazy  boy  will 
never  have  a  strong  body  or  brain  because  he 
will  not  use  them. 

What  the  nerves  do. 

There  are  two  kinds  of  nerves.  One  kind 
carries  messages  to  the  brain  and  the  other 
carries  messages  from  the  brain  out  to  the 
body.  Ends  of  nerves  are  found  under  the 
skin  all  over  the  surface  of  the  body.  When- 
ever the  skin  is  touched  even  by  a  feather,  a 
report  is  sent  in  at  once  to  the  brain.  In  this 
way  the  mind  is  warned  at  once  of  any  danger 
that  might  come  to  the  body.  If  it  were  not 
for  these  nerves,  you  could  put  your  hand  into 
the  fire  or  cut  off  a  finger  and  it  would  not 
hurt.  I  fear  we  would  not  take  very  good 
care  of  our  bodies  if  it  did  not  pain  when  we 
are  scratched  or  cut  or  bruised  or  burned. 
These  nerves  have  other  uses  too,  but  we  will 
tell  you  about  that  in  the  next  chapter. 

The  other  nerves  are  used  to  carry  mes- 
sages from  the  brain  out  to  the  muscles. 
When  I  want  to  move  my  big  toe,  the  brain 
sends  an  order  all  the  way  down  to  a  muscle 
there  and  the  toe  is  moved.  We  cannot  feel 
anything  going  along  the  nerve,  but  we  know 


BRAIN,  SPINAL   CORD,  AND   NERVES    117 

that  if  this  nerve  were  cut  in  two  we  could  not 
make  the  toe  move,  no  matter  how  hard  the 
mind  would  try. 

What  the  spinal  cord  does. 

The  spinal  cord  carries  messages  back  and 
forth  between  the  body  and  the  brain  ;  but  it 
does  more  than  that.  It  often  takes  part  of 
the  work  of  the  brain  upon  itself  and  sends 
out  orders  to  the  muscles  without  telling  the 
brain  anything  about  it.  If  you  put  your  hand 
on  a  hot  stove,  the  nerves  send  in  a  message 
to  the  spinal  cord,  and  right  away  an  order  is 
sent  back  to  the  muscles  of  the  arm  to  pull 
the  hand  away.  When  you  make  up  your 
mind  to  take  a  walk,  the  brain  sends  an  order 
to  the  muscles  of  the  legs  to  begin  work  ;  but 
after  you  are  started,  the  spinal  cord  will  look 
after  the  walking,  and  the  mind  can  be  free  to 
think  of  other  things. 

The  upper  part  of  the  spinal  cord  is  thicker 
than  the  rest  of  it.  This  thick  part  is  just  in- 
side the  skull.  In  picture  33  you  can  see  the 
hole  where  the  spinal  cord  enters  the  base  of 
the  skull.  This  part  of  the  cord  is  very  im- 
portant. It  looks  after  our  breathing  and  the 
beating  of  our  hearts.  We  may  stop  breath- 
ing for  a  little  while,  but  it  will  soon  start 


n8          FIRST   BOOK   OF    PHYSIOLOGY 

again  in  spite  of  all  we  can  do.  The  mind 
cannot  stop  the  heart  at  any  time. 

If  any  serious  accident  should  happen  to 
this  part  of  the  spinal  cord  death  would  follow 
at  once,  for  the  heart  and  lungs  would  stop 
their  work. 

You  see  that  the  whole  spinal  cord  is  very 
useful  to  us.  It  watches  over  our  bodies  all 


33.— A  skull. 

day  and  night.  It  is  always  on  guard  to  keep 
us  from  getting  hurt.  It  leaves  the  mind  free 
to  study  and  think.  No  wonder  it  is  so  well 
protected  inside  a  strong,  bony  tube. 

Sleep. 

All  healthy  boys  and  girls  are  all  the  time 
doing  something.     Their  minds  are  at  work 


BRAIN,   SPINAL   CORD,  AND    NERVES     119 

all  day  and  their  bodies  are  active  in  work  or 
play.  The  brain  and  the  whole  body  must 
have  rest  or  they  will  soon  break  down.  We 
cannot  get  complete  rest  while  we  are  awake. 
When  we  are  in  sound  sleep  the  brain  is  not 
doing  anything,  and  the  body  is  doing  only 
enough  to  keep  us  alive  till  we  get  awake 
again.  The  heart  beats  slower  and  we  do  not 
breathe  so  often  when  we  are  asleep. 

You  must  have  plenty  of  sleep  during  the 
night  or  you  will  not  be  able  to  do  good  work 
the  next  day.  You  cannot  even  play  well  un- 
less you  have  had  a  good  sleep.  Most  people 
need  about  eight  hours  of  sleep  every  night. 
Children  should  sleep  nine  or  ten  hours  out 
of  every  twenty-four. 

Night  is  the  proper  time  for  sleep.  Babes 
and  young  children  need  to  sleep  some  in  day- 
time, but  the  boys  and  girls  who  read  this 
book  should  get  enough  of  good  sound  sleep 
in  the  night  so  that  they  can  be  wide  awake  all 
day.  A  sleepy  boy  is  not  of  much  account  in 
school  or  in  any  other  place. 

Habit. 

Most  things  are  hard  to  do  the  first  time  we 
try.  After  we  have  done  them  several  times 
they  become  much  easier,  and  by  and  by  the 


120          FIRST   BOOK   OF   PHYSIOLOGY 

way  we  do  things  and  the  way  we  act  become 
fixed  habits.  You  can  now  tie  your  shoe-* 
strings  without  thinking  about  it,  but  it  was  a 
task  for  you  at  first.  It  has  become  a  habit. 
The  way  a  man  ties  his  necktie  is  a  habit  with 
him,  and  it  is  hard  for  him  to  tie  it  in  any  other 
way. 

You  can  get  into  a  habit  of  always  being 
neat  and  clean  ;  of  having  good  lessons  every 
day  ;  of  always  being  pleasant  and  polite  ;  of 
always  being  on  time.  There  are  many  habits 
of  this  kind  that  every  boy  and  girl  should  try 
to  form.  If  you  will  try  them  till  they  become 
easy  then  they  will  be  a  habit  with  you,  and 
you  would  rather  follow  them  than  do  any 
other  way. 

It  is  easy  to  get  into  bad  habits,  and  then  it 
will  be  hard  to  get  away  from  them.  A  boy 
can  get  into  a  bad  habit  of  smoking  cigarettes, 
and  then  he  gets  an  appetite  for  it.  Then  the 
two  together  are  stronger  than  the  boy,  and 
he  will  not  quit  even  when  he  knows  his  bad 
habit  is  killing  him. 

Men  and  boys  get  into  the  habit  of  going 
"  down  town"  in  the  evenings.  Every  evening 
they  are  almost  sure  to  go  again.  They  get 
into  a  bad  habit  of  drinking,  and  keep  on 
going  from  bad  to  worse. 


BRAIN,  SPINAL   CORD,  AND   NERVES    121 

Every  boy  and  girl  should  try  to  have  many 
habits,  but  they  should  all  be  good  ones. 

It  is  easy  to  fall  into  bad  habits,  but  very 
hard  to  get  out  of  them. 

Skill. 

We  all  want  to  have  strong  muscles,  but  we 
want  them  to  be  well  trained,  too. 

When  the  muscle  will  do  just  what  the  mind 
wants  done,  it  is  a  trained  muscle.  Boys  and 
girls  should  try  hard  every  day  to  train  their 
muscles  to  do  things  well.  If  you  do  not 
train  them  they  will  always  be  awkward.  You 


34- — Before  and  after  long  practice. 

want  to  be  a  good  writer.  Then  you  must 
practise  every  day  to  get  the  muscles  of  your 
arm  and  fingers  trained.  The  last  page  in 
your  copybook  should  be  much  better  than 
the  first  one.  If  it  is  not,  then  you  are  not 
getting  any  good  out  of  your  practice  in 
writing.  Try  again,  and  think  all  the  time 
that  you  are  trying  to  get  your  muscle  to  obey 


122  FIRST   BOOK    OF    PHYSIOLOGY 

the  mind.  It  will  be  sure  to  do  so  if  you  will 
try  your  best  every  day. 

The  writing  in  this  upper  line  was  done  by 
a  little  girl  several  years  ago.  You  can  see  it 
was  hard  for  her  to  make  the  pen  go  right. 
She  went  right  on  doing  her  best,  and  to-day 
she  can  write  like  that  in  the  second  line. 

It  is  the  same  way  with  drawing.  You 
know  what  a  poor  picture  you  made  when  you 
first  tried  to  draw.  You  can  do  much  better 
now,  and  if  you  keep  on  trying,  your  mind 
and  hand  will  work  nicely  together. 

You  must  also  train  the  muscles  of  the 
mouth  if  you  want  to  speak  well.  It  is  hard 
for  little  children  to  learn  to  talk.  They  have 
to  try  for  a  long  time  before  they  can  get  the 
tongue  and  lips  to  move  just  right  to  make 
the  words.  Maybe  there  are  some  words  you 
do  not  say  very  well  yet.  Some  boys  and 
girls  mumble  their  words  so  that  you  can 
hardly  tell  what  they  are  trying  to  say.  They 
are  not  trying,  and  they  will  never  do  any 
better  till  they  do  try. 

A  story. 

More  than  two  thousand  years  ago  there 
lived  in  the  city  of  Athens  a  boy  whose  name 
was  Demosthenes.  He  was  not  as  bright  as 


BRAIN,   SPINAL    CORD,  AND    NERVES     123 

some  of  the  other  boys.  He  had  to  study 
very  hard  when  he  wanted  to  learn  anything. 
He  could  not  speak  his  words  plainly  and  he 
stammered.  He  was  awkward  in  his  motions, 
and  people  laughed  at  him. 

One  day,  after  he  had  grown  older,  he  went 
to  hear  a  famous  speaker  in  Athens.  There 
he  saw  what  wonderful  power  there  was  in  a 
great  speech  by  a  great  orator. 

He  thought  if  he  could  only  speak  like  that 
how  much  good  he  could  do  and  what  a  great 
man  he  would  be.  So  he  made  up  his  mind 
that  he  would  be  a  great  speaker.  He  went 
to  work  with  all  his  might,  and  one  day  he  got 
up  before  a  large  audience  to  make  his  first 
speech.  He  did  not  speak  well,  and  the  people 
laughed  at  him  and  hissed  him. 

Many  young  men  would  have  given  up  and 
not  tried  any  more.  Demosthenes  only  said 
that  he  would  try  all  the  harder,  and  now  he 
went  to  work  in  dead  earnest  to  make  his  mus- 
cles obey  his  mind  in  just  the  way  he  wished. 

Part  of  the  time  he  stood  before  a  mirror 
while  he  practised  speaking.  There  he  could 
see  for  himself  how  he  looked.  If  he  did  not 
stand  in  the  right  manner  or  if  he  moved  his 
hands  or  arms  in  an  awkward  way,  he  could 
see  it  in  the  mirror  and  would  correct  it. 


124          FIRST   BOOK   OF   PHYSIOLOGY 

He  had  a  bad  habit  of  holding  one  shoulder 
higher  than  the  other.  To  correct  this,  he 
would  stand  with  this  shoulder  just  under  the 
point  of  a  sharp  sword  while  he  was  speaking. 


35. — Demosthenes. 

Sometimes  he  would  shut  himself  up  for 
several  weeks  in  a  cave,  and  there  he  would 
practise  speaking. 

At  another  time  he  would  go  down  to  the 
seashore  and  fill  his  mouth  with  pebbles  and 
then  speak.  If  he  could  learn  to  talk  well 
with  pebbles  in  his  mouth,  then  surely  he  could 
do  much  better  when  he  took  them  out. 

The  above  picture  shows  him  at  this  prac- 
tice. 


BRAIN,   SPINAL    CORD,  AND    NERVES     125 

At  last  Demosthenes  became  the  most 
famous  speaker  in  the  world. 

Boys  and  girls  who  are  willing  to  go  through 
the  long  practice  that  is  needed  to  get  the 
body  to  obey  the  mind  may  also  be  famous  in 
one  way  or  another. 

Effect  of  alcohol  on  the  brain  and  nerves. 

You  must  use  your  brain  when  you  think. 
You  can  do  good  thinking  only  when  your 
brain  is  in  good  working  order.  You  have 
learned  that  a  muscle  must  have  food  that  it 
may  do  work.  It  is  the  same  way  with  the 
brain.  Every  time  the  heart  beats,  a  part  of 
the  blood  is  sent  to  the  head  to  feed  the  brain. 
Press  the  ends  of  your  fingers  against  either 
side  of  your  neck  and  you  can  feel  the  pulse 
of  the  blood  as  it  goes  up  through  a  large 
artery  to  the  head.  This  blood  must  be  good 
and  pure,  and  there  must  be  plenty  of  it.  Un- 
less this  is  so,  we  cannot  do  good  thinking. 
Anything  that  will  poison  the  blood  or  weaken 
it  will  have  a  bad  effect  on  the  brain. 

When  alcohol  gets  into  the  blood  some  of 
it  is  carried  at  once  to  the  head.  The  brain 
is  excited  by  it,  and  for  a  while  seems  to  be 
brighter  than  ever.  Very  soon  the  poison  of 
the  alcohol  is  sure  to  have  its  bad  effect.  The 


126  FIRST    BOOK   OF    PHYSIOLOGY 

brain  gets  stupid  and  will  not  work  again  till 
the  body  sends  it  good  blood. 

The  alcohol  has  also  been  spoiling  the  work 
of  the  stomach  and  lungs  and  liver  and  kid- 
neys so  they  cannot  make  good  blood.  In 
this  way,  too,  the  brain  is  both  starved  and 
poisoned. 

A  man  may  seem  to  get  over  the  bad  effects 
of  a  few  drinks  of  alcohol,  but  he  is  getting 
weaker  in  body  and  mind  all  the  time.  If  he 
keeps  on  drinking,  it  will  soon  be  plain  that  he 
cannot  think  about  anything  as  well  as  he  did 
before. 

Alcohol  makes  the  nerves  lose  their  power 
over  the  muscles.  The  hand  trembles  and 
loses  its  skill.  Such  a  person  can  not  write  as 
well  as  he  did  before.  He  cannot  even  raise 
a  glass  of  water  to  his  mouth  without  showing 
how  weak  and  unsteady  he  is.  Alcohol  has 
made  him  awkward  and  clumsy.  He  is  not 
wanted  any  more  to  do  fine  work  in  the  shops 
and  offices,  and  so  his  wages  go  down.  People 
do  not  trust  him,  and  he  cannot  get  a  good 
position. 

When  the  brain  becomes  very  weak  or  un- 
healthy, it  will  think  very  strange  things  and 
will  imagine  many  things  that  do  not  exist. 
Such  a  person  is  called  insane,  and  has  to  be 


BRAIN,  SPINAL   CORD,  AND   NERVES    127 

locked  up  to  keep  him  from  harming1  other 
people.  Alcohol  makes  many  men  insane. 

The  children  of  drunkards  are  often  weak 
and  diseased.  It  is  no  fault  of  the  children, 
but  they  have  to  suffer  for  the  alcohol  which 
their  father  drank. 

Not  many  boys  who  now  read  this  book 
ever  drank  any  whiskey  or  beer  or  wine,  but 
we  want  you  to  know  how  much  evil  it  is 
doing  to  many  older  people.  Now  is  the  best 
time  for  you  to  begin  to  be  an  able  and  healthy 
man.  Our  bodies  are  not  of  much  use  to  us 
without  a  good  brain,  spinal  cord,  and  nerves, 
and  we  know  that  alcohol  has  the  worst  kind 
of  an  effect  upon  the  whole  nervous  system. 

Effect  of  cigarettes  on  the  brain  and  nerves. 

Many  boys  who  would  not  think  of  drinking 
whiskey  are  doing  their  brains  and  nerves 
great  harm  by  smoking  cigarettes.  We  have 
shown  you  how  tobacco  will  poison  the  blood. 
It  is  this  kind  of  blood,  then,  that  must  feed  the 
brain.  A  cigarette  smoker  cannot  sleep  well 
at  night.  When  he  gets  up  in  the  morning  he 
does  not  feel  fresh  and  strong.  He  comes  to 
school  sleepy.  He  cannot  make  his  brain 
work,  for  it  is  poisoned  and  weak.  Of  course, 
he  cannot  keep  up  in  his  school-work. 


128          FIRST   BOOK   OF   PHYSIOLOGY 

A  story. 

In  one  of  the  schools  of  a  Western  towit 
was  a  bright  boy  eleven  years  of  age.  He  had 
started  to  school  when  he  was  six,  and  was 
promoted  every  time  with  high  grades.  His 
teachers  aH  praised  him  for  his  good  deport- 
ment and  good  lessons.  The  boys  and  girls 
all  liked  him  because  he  was  smart  and  was 
good  at  running,  jumping,  and  playing  ball. 
He  was  now  about  half-way  through  the  fifth 
grade  when  something  began  to  go  wrong. 
Neither  the  teachers  nor  the  scholars  could 
guess  what  the  matter  was.  The  boy  began 
to  be  careless  about  himself.  He  would  go 
about  with  his  hat  pulled  down  over  his  eyes 
and  would  not  look  square  at  you  when  you 
would  speak  to  him.  His  clothes  and  shoes 
were  not  brushed,  and  he  walked  in  a  slouchy 
manner. 

In  the  school-room  he  did  not  give  attention, 
but  spent  much  of  his  'time  looking  about  or 
just  staring  without  looking  at  anything.  At 
other  times  he  would  start  some  mischief  that 
would  annoy  the  other  scholars,  and  when  the 
teacher  would  try  to  correct  him  he  would 
only  grunt  out  some  impolite  reply  and  then 
sulk  in  his  seat. 

What  in  the  world  had  gone  wrong  ! 


BRAIN,   SPINAL   CbRD,  AND    NERVES     129 

The  boy  would  try  sometimes  to  master 
himself.  He  would  try  to  force  himself  to 
study  and  act  as  he  used  to  do,  but  he  could 
not  keep  it  up. 

After  this  had  gone  on  for  several  weeks, 
he  stayed  one  evening  after  school  of  his  own 
accord.  When  all  the  children  had  gone,  he 
came  up  to  the  teacher  and  said  that  he 
wanted  to  tell  her  something.  He  told  her 
that  he  once  smoked  a  few  cigarettes  just  to 
see  what  it  was  like,  and  after  he  had  learned, 
he  wanted  to  smoke  them  all  the  time.  He 
said  he  could  see  that  if  he  did  not  stop,  they 
would  ruin  him,  and  he  wanted  to  quit. 

His  teacher  always  liked  to  do  anything  for 
the  good  of  her  scholars,  and  she  was  very 
glad  when  the  boy  came  right  out  and  told 
her  all  about  it.  He  promised  that  he  would 
come  to  her  every  day  for  one  month  and  tell 
her  that  he  had  not  used  tobacco  in  any  way. 

He  was  a  manly  little  fellow  and  kept  his 
word.  He  now  thinks  that  this  changed  his 
whole  life.  If  he  had  gone  on  with  cigarettes, 
it  is  almost  certain  that  he  would  soon  have 
quit  school,  and  would  have  gone  with  bad 
company  and  become  a  drunkard  at  last. 

This  all  happened  a  number  of  years  ago. 
The  boy  passed  on  through  every  grade  in 


130  FIRST    BOOK   OF    PHYSIOLOGY 

school  and  then  graduated  from  college.  He 
is  now  a  useful  and  successful  man,  but  hfe 
never  forgets  that  evening  in  school  when  he 
had  the  courage  to  quit  smoking  cigarettes. 

Questions. 

1 .  Describe  the  brain. 

2.  Tell  about  the  spinal  cord. 

3.  What  is  the  use  of  nerves  ? 

4.  How  are  nerves  like  telephone  wires  ? 

5.  What   does   the   brain    do  ?     How    can    it   be    made 
strong  ? 

6.  What  are  the  two  kinds  of  nerves  and  what  does  each 
do? 

7.  What  does  the  spinal  cord  do  ? 

8.  Why  do  we  need  sleep  ?     How  much  sleep  should  we 
have  ? 

9.  Tell  all  you  can  about  habit. 

10.  How  can  you  learn  to  write  and  draw  and  speak  well  ? 

1 1 .  Tell  the  story  of  Demosthenes. 

12.  How  does  alcohol  harm  the  brain  and  nerves  ? 

13.  How  does  tobacco  harm  the  brain  and  nerves  ? 

14.  Tell  the  story  of  the  boy  who  smoked  cigarettes. 


CHAPTER    XI 

THE  SENSES. 

WE  have  five  senses.  They  are  seeing, 
hearing,  feeling,  tasting,  and  smelling. 

The  mind  uses  these  senses  to  find  out  about 
things  it  wants  to  know.  If  you  would  lose 
all  your  senses,  you  could  not  tell  whether  you 
were  alive  or  not.  When  I  hand  you  some- 
thing and  ask  you  to  tell  me  all  you  can  find 
out  about  it,  you  look  at  it,  then  maybe  you 
tap  it  and  listen  to  the  sound,  then  you  feel  it 
or  taste  and  smell  it.  This  is  all  we  can  do 
with  the  senses,  but  all  that  we  know  was  first 
learned  in  this  way. 

The  eyes. 

The  eye  is  the  shape  of  a  ball.  It  is  set  in 
a  bony  socket  on  a  bed  of  fat.  It  is  covered 
with  a  tough  coat  called  the  white  of  the  eye. 
In  front  it  is  as  clear  as  glass,  so  the  light  can 
get  in.  A  little  farther  back  is  a  curtain, 
which  in  some  people  is  black  and  in  others 
blue  or  gray. 

In  the  centre  of  the  curtain  is  a  round  hole, 


I32 


FIRST   BOOK   OF   PHYSIOLOGY 


that  gets  large  when  the  light  is  dim  and  small 
when  the  light  is  bright.     Look  into  a  mirror  ! 


30. — The  eyes. 


and  see  how  the  curtain  works  when  you  sud- 
denly make  the  light  bright  and  then  dim. 
The  light  goes  through  this  hole  and  then 


37. — Section  of  eye. 

on  through  a  lens  that  you  can  see  in  picture 
37.      This   lens   acts  just   like  the  glass    in 


THE    SENSES  133 

your  microscope  and  makes  a  picture  on  the 
back  part  of  the  eye.  The  nerve  then  carries 
it  to  the  brain,  and  in  that  way  we  see. 

How  we  move  the  eyes. 

Muscles  are  fastened  to  the  eyeball  on  the 
top  and  bottom  and  at  the  sides.  When  they 
pull,  they  roll  the  eye  up  or  down  or  sideways. 
This  is  a  great  help  to  us  when  we  want  to 
look  around.  You  can  see  the  whole  side  of 
a  room  without  moving  your  head. 

How  the  eye  is  protected. 

The  eyes  are  very  delicate  and  can  be  easily 
harmed.  Curtains  called  eyelids  are  made  to 
close  over  the  front  of  the  eye,  and  we  wink 
whenever  there  is  danger  of  dust  or  dirt  get- 
ting into  the  eye. 

The  eyebrows  also  protect  the  eyes  by 
keeping  sweat  from  running  down  into 
them. 

Just  above  the  eyes  are  little  sacs  that  gather 
from  the  bloocl  a  liquid  called  tears.  A  little 
of  this  liquid  keeps  running  out  over  the  eyes 
all  the  time  to  keep  them  moist  and  wash 
away  any  specks  of  dust.  At  the  inner  cor- 
ner of  the  eye  is  a  small  tube  that  carries  the 
tears  into  the  nose.  When  you  laugh  real 


134          FIRST   BOOK   OF   PHYSIOLOGY 

hard  or  cry,  the  tears  come  so  fast  that  the 
tube  cannot  carry  them  off,  and  they  run  over 
on  the  cheeks. 

Care  of  the  eyes. 

Most  people  say  they  would  not  give  up 
their  eyes  for  the  world,  and  yet  they  use  them 
so  badly  that  we  would  think  they  did  not  care 
for  them. 

You  should  never  look  at  the  sun  or  any 
bright  light.  Do  not  try  to  read  out  in  the 
bright  sunlight.  When  you  use  a  light  that  is 
too  strong,  the  sight  will  get  dim. 

It  is  just  as  bad  to  read  when  the  light  is  too 
weak.  Do  not  try  to  read  in  the  dusk  of  the 
evening  or  in  the  dark  corner  of  a  room  or 
by  any  weak,  flickering  light. 

Do  not  sit  facing  the  light  when  you  read, 
but  let  it  fall  down  over  your  shoulders  upon 
the  book. 

Do  not  read  while  you  are  lying  down. 
People  have  made  themselves  blind  by  reading 
in  this  way. 

Alcohol  and  tobacco  have  a  very  bad  effect  on 
the  eyes.  Alcohol  affects  the  nerve,  so  it  can- 
not carry  a  true  picture  back  to  the  brain,  and 
it  weakens  the  other  delicate  parts  of  the  eye. 
Cigarettes  have  had  such  a  bad  effect  on  the 


THE   SENSES  135 

eyes  of  boys  that  the  doctor  told  them  he 
could  not  keep  them  from  going  blind  unless 
they  would  quit  smoking. 

If  you  have  good  eyes  and  take  care  of 
them,  they  will  be  good  for  nearly  all  your 
lifetime. 

The  ear. 

We  would  lose  a  great  deal  in  this  world  if 
we  had  no  eyes,  but  it  would  be  about  as  bad 


38.— The  ear. 

if  we  had  our  eyes,  but  had  no  ears.  If  you 
had  to  give  up  your  eyes  or  your  ears,  which 
would  you  let  go  ?  Think  carefully  before  you 
answer. 

The  part  of  the  ear  outside  the  head  catches 
sound  and  sends  it  into  the  ear.     People  who 


136  FIRST    BOOK    OF    PHYSIOLOGY 

cannot  hear  very  well  put  their  hands  back  of 
the  ears  to  catch  more  sound. 

The  rest  of  the  ear  is  just  the  size  and  shape 
that  you  see  in  picture  38.  One  of  these  is 
on  each  side  of  the  head  in  the  bone  of  the 
skull. 

Waves  of  sound  come  in  where  you  see  the 
arrow  in  the  picture.  These  waves  shake  the 
ends  of  the  nerves  at  the  other  end  of  the  ear, 
and  the  nerves  then  carry  the  sound  back  to 
the  brain. 

The  ear  and  throat. 

In  the  picture,  on  the  right  of  it,  you  can 
see  the  tube  that  connects  the  ear  with  the 
throat.  We  cannot  hear  well  unless  this  tube 
is  kept  open.  Often,  when  you  have  a  cold,  it 
gets  stopped  up,  and  then  you  have  earache 
or  a  roaring  sound  in  the  ear.  You  can  often 
open  the  tube  by  swallowing,  and  then  the 
roaring  stops. 

Care  of  the  ears. 

The  ear  tries  to  protect  itself,  but  often  we 
have  to  help  it.  The  tube  that  leads  into  the 
ear  is  lined  with  hairs  and  wax.  These  keep 
out  insects  and  dirt.  Sometimes,  though,  a 
bee  or  bug  will  creep  away  into  the  ear  and 


THE    SENSES  137 

cause  a  great  deal  of  pain  and  fright  ;  but  the 
doctor  can  soon  pull  it  out. 

The  ear  should  not  be  filled  tight  with 
cotton.  If  any  cotton  is  used,  it  should  be 
very  loose  and  only  at  the  entrance  of  the  ear. 

Very  loud  sounds  injure  the  ear  and  often 
make  people  deaf.  When  you  are  expecting 
a  very  loud  sound,  it  is  a  good  plan  to  hold 
the  mouth  wide  open  or  close  the  mouth  and 
put  your  fingers  in  your  ears. 

It  is  wrong  to  pick  the  ear  with  an  ear-spoon 
or  with  anything  else,  or  to  put  any  kind  of  a 
liquid  into  it  unless  it  is  the  order  of  the 
doctor.  The  ear,  like  the  eye,  is  too  valuable 
and  delicate  to  be  tampered  with. 

Feeling. 

We  can  learn  a  great  deal  about  things  by 
the  sense  of  touch.  You  will  find  it  an  in- 
teresting game  if  you  will  blindfold  one  of 
your  playmates  and  then  put  different  things 
into  his  hands  and  see  if  he  can  tell  what  they 
are.  He  can  tell  that  it  is  an  egg,  or  a  stone, 
or  a  pencil,  or  a  marble,  and  do  it  all  by  feeling. 
Once  in  a  while  he  will  make  a  bad  mistake, 
and  that  is  where  the  fun  comes  in. 

Blind  children  learn  to  read  with  the  fingers. 
On  the  pages  of  their  books  the  letters  are 


138  FIRST   BOOK   OF    PHYSIOLOGY 

raised,  and  by  running  their  fingers  over  them 
they  can  tell  what  the  words  are.  One  girl, 
whose  name  is  Helen  Kellar,  can  neither  see 
nor  hear,  and  yet  she  can  tell  what  you  are 
saying  by  holding  her  fingers  on  your  lips 
while  you  are  talking. 

Taste  and  smell. 

The  nerves  of  taste  are  in  the  tongue,  and 
the  nerves  of  smell  are  in  the  nose. 

These  two  senses  do  not  tell  us  so  much  as 
any  one  of  the  other  three,  but  they  are  very 
useful. 

They  guard  the  gateways  to  the  stomach 
and  the  lungs.  They  warn  us  against  bad 
food  and  bad  air.  When  food  is  spoiled,  our 
nerves  of  taste  and  smell  will  tell  us  not  to 
eat  it.  When  we  come  in  out  of  fresh  air, 
our  nerves  of  smell  will  tell  us  if  the  air  in 
the  room  is  bad. 

These  two  senses  are  also  very  useful  in 
other  ways.  Salt  may  look  just  like  sugar^ 
but  the  taste  will  soon  tell  us  which  it  is. 

These  nerves  are  often  spoiled  by  misuse. 
Alcohol  and  tobacco  will  make  them  so  blunt 
that  they  will  be  of  no  use,  and  then  they 
cannot  give  any  warning  against  bad  food  and 
impure  air. 


THE   SENSES  139 

Questions. 

1 .  What  are  the  five  senses  ? 

2.  Describe  the  eye. 

3.  How  can  we  move  our  eyes  ? 

4.  How  is  the  eye  protected  ? 

5.  What  are  some  things  that  injure  the  eyes  ? 

6.  How  do  we  hear  ? 

7.  How  is  the  ear  joined  to  the  throat  ? 

8.  How  can  we  care  for  our  ears  ? 

9.  Which  one  of  the  senses  do  blind  children  use  when 
they  read  ? 

10.  What  can  we  find  out  by  the  sense  of  taste  and  smell  ? 


INDEX 


A 

PAGE 

Air  82 

Air-sacs    79 

Albinoes   99 

Alcohol : 

Appetite   for 41 

Effect  on  muscle     37 

Effect  on  heart 66 

Effect  on  white    corpuscles 73 

Effect  on  warmth  of  body 92 

Effect  on  skin 104 

Effect  on  liver   109 

Effect  on  brain  and  nerves 125 

Effect  on  eyes    134 

Appetite : 

Use  of 40 

Recipe  for 41 

Arteries    67 

B 

Bathing 101 

Beer    '. 38 

Effect  on  heart 66 

Bee-sting   -. 98 

Bile    55,57 

Bleeding 67,  73 

141 


142  INDEX 


Change  in  lungs  ..................................  79  > 

Clot  of  ............................................  73 

Effect  of  deep  breathing  on  .......................  88 

In  bones  ..........................................  27 

Liquid  part  of  ....................................  73 

Quantity  of  .......................................  64 

Bones  : 

Broken    ..........................................  25 

Care  of  ..........................................  27 

Change  in  shape  ..................................  24 

Composition    of  ...................................  24 

Experiment  with  ..................................  25 

Growth  of  ...............  :  ........................  26 

Kinds    of  .........................................  20 

Largest   in   body  ..................................  19 

Of   hand  .........................................  18 

Brain  ................................................  1  1  1 

Work    of  ......................................  in,  115 

Breathing     .........................................  75,  107 

Effect  of  tight  dressing  on  ........................  88 

Frequency   of  .....................................  86 

Of  pure  air  .......................................  83 

Use   of  ..........................................  75,  77 


C 

Candle : 

Experiment   with 75,  84 

Capillaries : 

Number   of 69 

Use  of 69 

Carbon   dioxide 81,  107 


INDEX  143 

PAGE 

Cartilage    22 

Cigarettes    36 

And  athletics 87 

Effect  on  brain  and  nerves 127 

Effect  on  eyes    134 

Effect  on  heart    66 

Effect  on  lungs   81,  86 

Clean  clothing 102 

Clear    skin 103 

Corns 95 

Corpuscles : 

Red    70 

White    .                                                                            ...  71 


D 

Deep    breathing 88 

Digestion : 

In  intestines 55 

In   stomach 53 


E 

Ear    135 

Care  of 136 

Eating : 

Manner   of 60 

Enamel  on  teeth 49 

Epidermis    99 

Excretion     107 

Eyes    131 

Care    of 134 


144  INDEX 

PAGE 

Fat     43 

Feeling     137 

Femur 19 

Food: 

Five  kinds 43 

In  blood 73 

Its  three  uses 42 

Plain     61,  103 

Warmth  from 72 

Framework : 

Advantage  of 18 

Kinds   of 17 

Of  monkey 17 

G 

Gall-bladder    55 

Gastric  j  uice 52,  58 

Germs  of  disease 82 

Gullet    51 

H 

Habit    119 

Hair    96 

Care  of 97 

Health : 

Advantage  when  good 12,  16,  38 

When  good 16 

Heart    64 

Care  of  66 

Structure   of 65 

Work    of..  65 


INDEX  145 

I  PAGE 

Intestines   54 

Description    of 55 

Juices   in    55 

Section  of  56 

Two  kinds : 55 

Joints :  j 

How  made 21 

Kinds 21 

Use    of 20 

K 
Kidneys    109 

L 

Lime  in  bone 24 

Liver : 

Work    of 57,  109 

Lungs    78,  107 

Air-tubes    in 78 

Capacity  of 87 

Work  of 79,  80 

Manners :  M 

At  table 46 

Movements  of  eyes 133 

Muscles : 

About  the  mouth 30 

Care  of 35,  37 

How    caused    to   move 34 

How  cause  movement 32,  34 

10 


146  INDEX 

Muscles :  PAGB 

In  the  arm 3 :. 

Nature   of 31 

Of  eye 133 

Use  of 29,  31 

N 

Nails   96 

Nerves    101,  1 13,  1 14,  1 15 

Of  feeling 101 

Use  of 1 16 

Nicotine  36,  81 

0 

(Esophagus   51 

Oxygen     76,  89 

P 

Pancreas     55 

Pancreatic  juice 55,  56 

Physiology : 

Why   studied 1 1 

Its  three  parts 13 

Protection  of  eyes 133 

Proteid   43 

Pulse     67 

Counting  the 68 

Effects  of  exercise  on 69 

Pure    air 82 

1 

Red  corpuscles 70 

Size  and  shape 71 

Use  of 71 


INDEX  147 


S 
Saliva :  PAGK 

Its    use 51 

Scarf-skin    95,  96,  99 

Sebaceous  glands 100 

Shallow  wells 44 

Skill     121 

Skin     95 

As  a  protection 97 

Color    of 99 

Section  of 100 

Two  layers  of 95 

Sleep   118 

Smell 138 

Soap-bubbles  87 

Special    senses 131 

Spinal    cord 112 

Use  of 117 

Starch     43 

Stomach : 

Care  of 54 

Change  of  food  in 52 

Description    of tj2 

Stories : 

Of  a  boy 128 

Of   Demosthenes 122 

Of  four  boys : 61 

Of  six  men 93 

Swallowing   5! 

Sweat    90,  91 

Sweat-pores    .  101 


148  INDEX 

T  PAGE 

Taste I3*i| 

Teeth : 

Care  of 50 

Number   of 48 

Structure  of 49 

Use  of 48 

Temperature  of  body 89,  90 

Tendons   32 

Tobacco    36 

Effect  on  heart    66 

Effect  on  skin    105 

Tobacco  heart 66 

True    skin 95,  99 

Typhoid    fever 45 

V 

Veins    69 

Location  and  use 70 

Ventilation  83 

During   sleep 85 

W 

Warmth  of  body 89 

Water   43 

Abundance  of 44 

Hydrant    46 

Ice   in 45 

In  breath 108 

In  wells 44 

Water-j  ug   91 

Wells    44,  45 

White  corpuscles 71 

Windpipe   77 


£  A 

f  C  .   V^tyP  ( 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


